Hardenable self-supporting structures and methods

ABSTRACT

Compositions, particularly for forming dental products, having a hardenable self-supporting structure with sufficient malleability to be subsequently customized into a second shape and then hardened, and methods.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 12/250,309, filed Oct.13, 2008, now allowed, which is a divisional of U.S. Ser. No.10/219,398, filed Aug. 15, 2002, issued as U.S. Pat. No. 7,674,850,which claims the benefit of U.S. Provisional Application Ser. No.60/312,355, filed on Aug. 15, 2001, the entirety of which areincorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to materials, particularly dental materials, andmethods of making and using. These materials have sufficient internalstrength to be formed into a desired shape that can be maintained duringtransportation and storage and with sufficient malleability to besubsequently customized into a second shape and then hardened. Thesematerials can be used in a variety of applications, including oralprosthetic devices such as inlays, onlays, veneers, temporary crowns,permanent crowns, bridges, as well as fillings, orthodontic appliances,tooth facsimiles or splints, and dental impression trays.

BACKGROUND

Restorative dentistry is an important market in today's dental industry.In particular, tooth repair with temporary and permanent crowns is acommon procedure, typically requiring multiple dental appointments.Current technology uses pastes, two-part powder/liquid systems,preformed metal temporary crowns, and ceramic or porcelain/metalpermanent crowns.

Currently available polymerizable resins are typically free radicallypolymerizable monomers (e.g., acrylates, methacrylates, andacrylamides). These are used together with initiator systems thattypically include reducing agents, such as tertiary amines, andoxidizing agents, such as peroxides, as accelerators or activators forfree radical polymerization and control of the rate of polymerization.

A typical procedure for making a provisional (i.e., temporary) dentalrestorative involves the following steps. Initially, an alginateimpression is taken before preparing the teeth. The impression isrinsed, set aside, and wrapped in a moist paper towel. The teeth arethen prepared and the correct shade of acrylic powder is selected tomatch the natural teeth. An acrylic liquid resin and the acrylicpolymeric powder, one of which includes a reducing agent and the otherof which includes an oxidizing agent, are mixed together and placed inthe impression. The impression is placed aside until the compositionthickens and forms a dull appearance (approximately 45-60 seconds).Meanwhile, the prepared teeth and surrounding tissue are coated with apetroleum jelly, which ensures easy removal of the acrylic temporaryfrom the preparation and protects the teeth and tissue from irritationby the acrylic mixture. The impression with the acrylic mixture isseated in the mouth and held in place for a sufficient time to allow itto harden to a removable state. The acrylic material is removed from theimpression and gross excess acrylic is trimmed. The acrylic material isplaced in and out of the mouth while the acrylic material is in arubbery state. The acrylic material is removed from the mouth and setaside until the acrylic is fully cured. The fit of the acrylicrestorative is checked and adapted to fit, if necessary. Excess acrylicis trimmed with an acrylic bur or stone and polished to a smooth finish.The acrylic temporary is then cemented into place.

It would be desirable to eliminate the initial mixing of the liquidresin and the polymeric powder and thereby create such prostheticdevices more efficiently. It would also be desirable to eliminate theimpression-taking step. Dental waxes, commonly used for takingimpressions in the mouth, exhibit many desirable properties for creatingdevices that are customized to a patient's mouth. These propertiesinclude malleability, low memory, sufficient strength to beself-supporting, and the thermal and rheological properties shown inFIG. 1. These wax (e.g., paraffin) materials typically have meltingpoints near 55° C., with softening transitions near 40° C. Elastic andviscous moduli G′ and G″ are approximately 10⁶ Pascals (Pa) at 25° C.,sufficiently low to be easily deformed without being tacky. Althoughthese materials exhibit desirable properties for creating devicescustomized to fit a patient's mouth, they are not hardenable (e.g.,through polymerization), nor do they possess desirable properties suchas compressive strength and wear resistance. As a result, thesematerials are not suitable for dental prosthetic applications.

U.S. Pat. No. 6,057,383 (Volkel et al.) discloses a dental materialbased on polymerizable waxes, wherein the materials are malleable andcurable; however, they are based on little or no filler, typically 0-60%by weight, and high amounts of waxes, typically more than 20% by weight.As such, these materials have generally poor mechanical properties, suchas flexural strength and wear resistance. Other thermoplastic moldingcompounds have been prepared, but these are typically highly viscousabove their melting point (T_(m)), and somewhat elastic below T. due tothe high molecular weight of the included polymer. Moreover, thesecompositions must typically be warmed significantly above roomtemperature before becoming malleable.

It would be desirable to have highly filled materials that can bepreformed into a desirable shape yet be sufficiently malleable,particularly at room temperature or body temperature, to form acustom-shaped device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Rheological response of dental wax (Baseplate Wax All-Season #2Pink, Patterson Dental Supply, St. Paul, Minn.). Solid symbols representelastic modulus G′, while open symbols represent viscous modulus G″.

FIG. 2. Rheology of Comparative Example 1 (squares) and Example 1(circles). Solid symbols represent G′, while open symbols represent G″.

SUMMARY

The present invention provides a composition that includes a resinsystem, a filler system, and an initiator system. The composition is inthe form of a hardenable, self-supporting (i.e., free-standing)structure having a first shape. The self-supporting structure hassufficient malleability to be reformed into a second shape, therebyproviding for simplified customization of a device, e.g., simplifiedcustomized fitting of a dental prosthetic device. Once reformed into asecond shape, the composition can be hardened using, for example, a freeradical curing mechanism under standard photopolymerization conditionsto form a hardened composition with improved mechanical properties.Significantly, for the compositions of the present invention uponhardening the structure in the second shape, the hardened structure doesnot need an additional veneering material.

Herein, the “resin system” can include one or more resins, each of whichcan include one or more monomers, oligomers, and/or polymerizablepolymers.

The term “self-supporting” means that the composition is dimensionallystable and will maintain its shape (e.g., preformed shape of a crown)without significant deformation at room temperature (i.e., about 20° C.to about 25° C.) for at least about two weeks when free-standing (i.e.,without the support of packaging or a container). Preferably, thecompositions of the present invention are dimensionally stable at roomtemperature for at least about one month, and more preferably, for atleast about six months. Preferably, the compositions of the presentinvention are dimensionally stable at temperatures above roomtemperature, more preferably up to about 40° C., even more preferably upto about 50° C., and even more preferably up to about 60° C. Thisdefinition applies in the absence of conditions that activate theinitiator system and in the absence of an external force other thangravity.

The term “sufficient malleability” means that the self-supportingstructure is capable of being custom shaped and fitted, for example, toa patient's mouth, under a moderate force (i.e., a force that rangesfrom light finger pressure to that applied with manual operation of asmall hand tool, such as a dental composite instrument).

The unique combination of highly malleable properties (preferablywithout heating above room temperature or body temperature) beforehardening (e.g., cure) and high strength (preferably, a flexuralstrength of at least about 25 MPa) after hardening provides acomposition with numerous potential applications. These applicationsinclude, but are not limited to, dental restoratives and dentalprostheses, including, but not limited to, temporary, intermediate, andpermanent crowns and bridges, inlays, onlays, veneers, implants,dentures, and artificial teeth, as well as dental impression trays,orthodontic appliances (e.g., retainers, night guards), tooth facsimilesor splints, maxillofacial prosthesis, and other customized structures.The compositions of the present invention can also be used as fillingmaterials (particularly packable materials), for example. A preferredembodiment of the invention is a composition that includes a resinsystem including a crystalline component, greater than 60 percent byweight (wt-%) of a filler system (preferably, greater than 70 wt-% of afiller system), and an initiator system, wherein the composition is inthe form of a hardenable self-supporting structure having a first shape.The self-supporting structure has sufficient malleability to be formedinto a second shape, preferably at a temperature of about 15° C. to 38°C. (more preferably, about 20° C. to 38° C., which encompasses typicalroom temperatures and body temperatures, and most preferably, at roomtemperature). Advantageously, the compositions of the present inventiondo not need to be heated above body temperature (or preferably, evenabout room temperature) to become malleable.

Typically and preferably, at least a portion of the filler systemcomprises particulate filler. Preferably, in this and various otherembodiments, if the filler system includes fibers, the fibers arepresent in an amount of less than 20 wt-%, based on the total weight ofthe composition.

The crystalline component provides a morphology that assists inmaintaining the self-supporting first shape. This morphology includes anoncovalent structure, which may be a three-dimensional network(continuous or discontinuous) structure. If desired, the crystallinecomponent can include one or more reactive groups to provide sites forpolymerizing and/or crosslinking If such crystalline components are notpresent or do not include reactive groups, such reactive sites areprovided by another resin component, such as an ethylenicallyunsaturated component.

Thus, for certain embodiments, the resin system preferably includes atleast one ethylenically unsaturated component. Preferred ethylenicallyunsaturated components are selected from the group consisting of mono-,di-, or poly-acrylates and methacrylates, unsaturated amides, vinylcompounds (including vinyl oxy compounds), and combinations thereof.This ethylenically unsaturated component can be the crystallinecomponent, although in certain preferred embodiments it isnoncrystalline.

The crystalline component can include polyesters, polyethers,polyolefins, polythioethers, polyarylalkylenes, polysilanes, polyamides,polyurethanes, or combinations thereof. Preferably, the crystallinecomponent includes saturated, linear, aliphatic polyester polyolscontaining primary hydroxyl end groups. The crystalline component canoptionally have a dendritic, hyperbranched, or star-shaped structure,for example.

The crystalline component can optionally be a polymeric material (i.e.,a material having two or more repeat units, thereby including oligomericmaterials) having crystallizable pendant moieties and the followinggeneral formula:

wherein R is hydrogen or a (C₁-C₄)alkyl group, X is —CH₂—, —C(O)O—,—O—C(O)—, —C(O)—NH—, —HN—C(O)—, —O—, —NH—, O—C(O)—NH—, —HN—C(O)—O—,—HN—C(O)—NH—, or —Si(CH₃)₂—, m is the number of repeating units in thepolymer (preferably, 2 or more), and n is great enough to providesufficient side chain length and conformation to form polymerscontaining crystalline domains or regions.

Alternative to, or in combination with, the crystalline component, thecomposition can include a filler that is capable of providing amorphology to the composition that includes a noncovalent structure,which may be a three-dimensional network (continuous or discontinuous)structure, that assists in the maintenance of the first shape.Preferably, such a filler has nanoscopic particles, more preferably, thefiller is an inorganic material having nanoscopic particles. To enhancethe formation of the noncovalent structure, the inorganic material caninclude surface hydroxyl groups. Most preferably, the inorganic materialincludes fumed silica.

Furthermore, the use of one or more surfactants can also enhance theformation of such a noncovalent structure. A particularly preferredcomposition includes, in addition to a resin system and an initiatorsystem, either a crystalline component, or a filler system that includesa nanoscopic particulate filler (preferably, both a micron-sizeparticulate filler and a nanoscopic particulate filler) and a surfactantsystem, or both a crystalline component and a filler system andsurfactant system. As used herein, a filler system includes one or morefillers and a surfactant system includes one or more surfactants.

Thus, another embodiment of the invention includes a composition thatincludes a resin system, a filler system at least a portion of which isan inorganic material having nanoscopic particles with an averageprimary particle size of no greater than about 50 nanometers (nm), asurfactant system, and an initiator system. The composition is in theform of a hardenable self-supporting structure having a first shape andsufficient malleability to be formed into a second shape, preferably ata temperature of about 15° C. to 38° C. In such preferred embodimentswith a surfactant system and nanoscopic particles, the resin systempreferably includes at least one ethylenically unsaturated component,and the filler system is present in an amount of greater than 50 wt-%.

In a preferred embodiment, a composition of the present inventionincludes a resin system that includes: a noncrystalline componentselected from the group consisting of mono-, di-, or poly- acrylates andmethacrylates, unsaturated amides, vinyl compounds, and combinationsthereof; and a crystalline component selected from the group consistingof polyesters, polyethers, polyolefins, polythioethers,polyarylalkylenes, polysilanes, polyamides, polyurethanes, polymericmaterials (including oligomeric materials) having crystallizable pendantmoieties and the following general formula:

wherein R is hydrogen or a (C₁-C₄)alkyl group, X is —CH₂—, —C(O)O—,—O—C(O)—, —C(O)—NH—, —HN—C(O)—, —O—, —NH—, or —O—C(O)—NH—, —HN—C(O)—O—,—HN—C(O)—NH—, or —Si(CH₃)₂—, m is the number of repeating units in thepolymer (preferably, 2 or more), and n is great enough to providesufficient side chain length and conformation to form polymerscontaining crystalline domains or regions, and combinations thereof. Thecomposition further includes greater than about 60 wt-% of a fillersystem and an initiator system, wherein the composition is in the formof a hardenable self-supporting structure having a first shape. Theself-supporting structure has sufficient malleability to be formed intoa second shape at a temperature of about 15° C. to 38° C. Preferably, ifthe filler system includes fibers, the fibers are present in an amountof less than 20 wt-%, based on the total weight of the composition.

In yet another preferred embodiment, a composition of the presentinvention includes a resin system comprising a crystalline compound ofthe formula:

wherein each Q independently comprises polyester segments, polyamidesegments, polyurethane segments, polyether segments, or combinationsthereof; a filler system; and an initiator system; wherein thecomposition is in the form of a hardenable self-supporting structurehaving a first shape and sufficient malleability to be formed into asecond shape.

The compositions of the present invention can be in the form of avariety of dental products, which can be in rope form (as for fillingmaterials), globular form, sheet form, or in the form of a preformedarticle, which is in a complex or semi-finished shape (as that of apreformed crown). Typically, the dental products referred to herein arein a hardenable form, but the term can also be used for the final dentalproduct in its hardened form.

Preferred dental products include a preformed crown, a preformed inlay,a preformed onlay, a preformed bridge, a preformed veneer, a preformedorthodontic appliance, a preformed maxillofacial prosthesis, a preformedtooth facsimile, or a preformed tooth splint. Alternatively, the dentalproduct can be a filling material (such as a packable material).Particularly preferred dental products include a preformed crown and apreformed bridge, and more preferably, a preformed crown.

In one preferred embodiment, the present invention provides a preformeddental crown that includes a composition including a resin system, afiller system, and an initiator system, wherein the composition is inthe form of a hardenable self-supporting structure having a first shapeand sufficient malleability to be formed into a second shape.

The present invention also provides a dental impression tray. Apreferred tray includes a resin system, a filler system, and aninitiator system in the form of a hardenable self-supporting structurehaving a first shape and sufficient malleability to be formed into asecond shape at a temperature of about 15° C. to 38° C. Preferably, thedental impression tray includes at least one structured surface.Preferably, the structured surface is formed by a porous substrate.Alternatively, the structured surface is a microreplicated surface.

The present invention also provides a method of preparing a composition.The method includes combining a resin system, a filler system, and aninitiator system to form a mixture; and forming the mixture into ahardenable self-supporting structure having a first shape; wherein thehardenable self-supporting structure having a first shape has sufficientmalleability to be formed into a second shape.

The present invention also provides a method of preparing a dentalproduct. The method includes: providing a composition comprising a resinsystem, a filler system, and an initiator system, wherein thecomposition is in the form of a hardenable, self-supporting, malleablestructure having a first semi-finished shape (e.g., that of a preformedcrown or preformed bridge); forming the self-supporting, malleablestructure into a second shape; and hardening the self-supportingstructure having the second shape to form a dental product. Preferably,forming the self-supporting, malleable structure into a second shapeoccurs at a temperature of about 15° C. to 38° C. Herein, forming theself-supporting, malleable structure into a second shape occurs under aforce that ranges from light finger pressure to that applied with manualoperation of a small hand tool, such as a dental composite instrument.

The present invention also provides a method of preparing a dental tray.The method includes: providing a composition comprising a resin system,a filler system, and an initiator system, wherein the composition is inthe form of a hardenable, self-supporting, malleable structure having afirst semi-finished shape of a preformed dental tray; forming theself-supporting, malleable structure into a second shape custom fit tothe patient; and hardening the self-supporting structure having thesecond shape to form a dental tray. Preferably, forming theself-supporting, malleable structure into a second shape occurs atemperature of about 15° C. to 38° C.

The present invention also provides a compound of the formula:

wherein each Q independently comprises polyester segments, polyamidesegments, polyurethane segments, polyether segments, or combinationsthereof.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The present invention provides a composition that includes a resinsystem, a filler system, and an initiator system in the form of ahardenable self-supporting (i.e., free-standing) structure having afirst shape, preferably the shape of a dental crown. The resin system(one or more resins), filler system (one or more fillers), and initiatorsystem (one or more initiators) are chosen such that: the compositioncan be relatively easily molded to form the initial self-supportingstructure; the self-supporting structure maintains its first shape atroom temperature for at least about two weeks (in the absence ofconditions that activate the initiator system and in the absence of anexternal force other than gravity), and the self-supporting structurehas sufficient malleability to be reformed into a second shape(preferably at a temperature of about 15° C. to 38° C., more preferably,at a temperature of about 20° C. to 38° C., and most preferably, at roomtemperature).

The compositions of the present invention are particularly well suitedfor preformed dental products. As used herein, a preformed dentalproduct is one that is provided to the dentist in the desiredsemi-finished shape (a first shape), which can then be modified (e.g.,molded, adapted, trimmed) for fit in a patient (a second shape). Herein,a semi-finished shape of a preformed article is the facsimile of whatthe final shaped article is to be, and is not the shape of a rope,globule, or sheet. This is described in greater detail below. Typically,this means that the compositions of the present invention have beenformed into a shape, preferably using a mold with a positive andnegative impression, and the resultant shaped material released from theshaping device, preferably a mold, without significant deformation.

Although the compositions of the present invention are particularlyuseful for preformed crowns and other preformed dental products having acomplex shape, they can be used as materials for preparing fillings,etc. The requirements for the latter are less stringent when it comes tomolding, removal from a mold, packaging, transportation, and the like,than is required for preformed crowns or other preformed dental articlesof a complex shape, typically because filling materials are provided tothe dentist in a rope form.

Generally, hardenable self-supporting compositions of the presentinvention have rheological properties similar to waxes below the waxes'melting points in that they can be relatively easily deformed (i.e.,they are malleable) and exhibit low elastic recovery. However, thecompositions of the present invention are not free-flowing fluids (i.e.,liquids) above their softening points. That is, the compositions of thepresent invention display appreciable mass flow under moderate (e.g.,hand) pressure, but not liquid flow above their softening points.

Typically, elastic and viscous dynamic moduli of hardenable compositionsof the present invention vary over a wide range. Furthermore, thehardenable compositions are typically largely free from tack.Preferably, the elastic dynamic modulus (i.e., elastic modulus) G′ is atleast about 100 kilopascals (kPa), more preferably, at least about 200kPa, and most preferably, at least about 1000 kPa, at a frequency ofabout 0.005 Hz. Preferably, the elastic modulus G′ is no greater thanabout 50,000 kPa, more preferably, no greater than about 10,000 kPa, andmost preferably, no greater than about 5000 kPa, at a frequency of about0.005 Hz. Preferably, the viscous dynamic modulus (i.e., viscousmodulus) G″ is at least about 50 kPa, more preferably, at least about200 kPa, and most preferably, at least about 1000 kPa, at a frequency ofabout 0.005 Hz. Preferably, the viscous modulus G″ is no greater thanabout 50,000 kPa, more preferably, no greater than about 10,000 kPa, andmost preferably, no greater than about 5000 kPa, at a frequency of about0.005 Hz.

The desired self-supporting (i.e., free-standing) structure ofhardenable compositions of the present invention can be maintained bycreating a morphology that includes a noncovalent structure, which maybe a three-dimensional network (continuous or discontinuous) structure.This can result from the use of a crystalline component in the resinsystem, or the use of one or more fillers, typically aided by one ormore surfactants, or the use of both a crystalline component and one ormore fillers optionally combined with one or more surfactants. Thesecomponents are discussed in more detail below.

With the appropriate initiator system, e.g., a free radicalphotoinitiator, hardenable compositions of the present invention can behardened (e.g., cured) to form the desired product. Preferably, theresultant hardened composition (i.e., the hardened structure) has aflexural strength of at least about 25 megapascals (MPa), morepreferably, at least about 40 MPa, even more preferably, at least about50 MPa, and most preferably, at least about 60 MPa.

For certain applications (e.g., crowns), the resultant hardenedcomposition is an enamel-like solid, preferably having a compressivestrength of at least about 100 MPa. For other applications, such asdental impression trays, materials with lower compressive strengths canbe used.

For certain applications (e.g., crowns), the resultant hardenedcomposition is an enamel-like solid, preferably having a diametraltensile strength of at least about 20 MPa. For other applications, suchas dental impression trays, materials with lower diametral tensilestrengths can be used.

For certain applications (e.g., crowns), the resultant hardenedcomposition is an enamel-like solid, preferably having a flexuralmodulus of at least about 1000 MPa. For other applications, such asdental impression trays, materials with lower flexural modulus can beused.

Resin System

Hardenable compositions of the present invention include a resin system.The resin system includes one or more hardenable organic resins capableof forming a hardened material having sufficient strength and hydrolyticstability to render them suitable for use in the oral environment.

As used herein, a resin includes one or more monomers, oligomers, and/orpolymerizable polymers, including combinations thereof. Although, inthis context oligomers and polymers are both used, the terms “polymer”and “polymeric” are used herein to refer to any materials having 2 ormore repeat units, thereby encompassing oligomers. Thus, unlessotherwise specified, polymers include oligomers. Furthermore, the termpolymer is used herein to encompass both homopolymers and copolymers,and the term copolymer is used herein to encompass materials with two ormore different repeat units (e.g., copolymers, terpolymers,tetrapolymers).

A preferred organic resin is hardenable (e.g., polymerizable and/orcrosslinkable), preferably by a free radical mechanism, and includesmonomers, oligomers, and/or polymers. The resin system includes areactive component (i.e., a component capable of polymerizing and/orcrosslinking), which may or may not be crystalline. Resin systems thatinclude noncrystalline reactive components may optionally include acrystalline component, which may or may not be reactive.

Preferably, at least some of the resin components include ethylenicunsaturation and are capable of undergoing addition polymerization. Asuitable resin preferably includes at least one ethylenicallyunsaturated monomer (i.e., includes at least one carbon-carbon doublebond).

Examples of suitable polymerizable resin components include: mono-, di-,or poly-(meth)acrylates (including acrylates and methacrylates) such asmethyl acrylate, methyl methacrylate, ethyl acrylate, isopropylmethacrylate, n-hexyl acrylate, stearyl acrylate, allyl acrylate,glycerol mono- and diacrylate, glycerol triacrylate, ethyleneglycoldiacrylate, diethyleneglycol diacrylate, triethyleneglycoldimethacrylate, 1,3-propanediol diacrylate, 1,3-propanedioldimethacrylate, trimethylolpropane triacrylate, 1,2,4-butanetrioltrimethacrylate, 1,4-cyclohexanediol diacrylate, pentaerythritoltriacrylate, pentaerythritol tetraacrylate, pentaerythritoltetramethacrylate, sorbitol hexaacrylate,bis(1-(2-acryloxy))-p-ethoxyphenyldimethylmethane,bis(1-(3-acryloxy-2-hydroxy))-p-propoxyphenyldimethylmethane,tris(hydroxyethylisocyanurate) trimethacrylate, 2-hydroxyethylmethacrylate, 2-hydroxypropyl methacrylate, tetrahydrofurfurylmethacrylate, ethylene glycol dimethacrylate, triethylene glycoldimethacrylate, bisGMA, ethoxylated bisphenolA diacrylate, ethoxylatedbisphenolA dimethacrylate, polyethylene glycol dimethacrylate, thebis-acrylates and bis-methacrylates of polyethylene glycols of molecularweight 200-500, copolymerizable mixtures of acrylated monomers such asthose of U.S. Pat. No. 4,652,274 (Boettcher et al.), and acrylatedoligomers such as those of U.S. Pat. No. 4,642,126 (Zador et al.);unsaturated amides such as (meth)acrylamides (i.e., acrylamides andmethacrylamides), methylene bis-acrylamide, methylenebis-methacrylamide, 1,6-hexamethylene bis-acrylamide, diethylenetriamine tris-acrylamide, and beta-methacrylamidoethyl methacrylate,diacetone acrylamide, and diacetone methacrylamide; urethane(meth)acrylates; and vinyl compounds such as styrene, diallyl phthalate,divinyl succinate, divinyl adipate, and divinylphthalate. Mixtures oftwo or more such materials can be used if desired in the resin system.

Preferably, the total amount of the resin system is at least about 10wt-%, more preferably, at least about 13 wt-%, and most preferably, atleast about 15 wt-%, based on the total weight of the composition.Preferably, the total amount of the resin system is no greater thanabout 60 wt-%, more preferably, no greater than about 50 wt-%, and mostpreferably, no greater than about 40 wt-%, based on the total weight ofthe composition.

The above-listed components are typically noncrystalline (i.e.,amorphous). The resin system can also include a crystalline component toimpart the noncovalent three-dimensional structure for maintaining theinitial preformed shape. This crystalline component may or may not havea reactive group capable of polymerizing (also including crosslinking)Preferably, the crystalline component is polymerizable. Preferably, thecrystalline component is polymeric (including oligomeric). Morepreferably, the crystalline component is a polymerizable polymericmaterial.

By “crystalline” it is meant that the material displays a crystallinemelting point at 20° C. or above when measured in the composition bydifferential scanning calorimetry (DSC). The peak temperature of theobserved endotherm is taken as the crystalline melting point. Thecrystalline phase includes multiple lattices in which the materialassumes a conformation in which there is a highly ordered registry inadjacent chemical moieties of which the material is constructed. Thepacking arrangement (short order orientation) within the lattice ishighly regular in both its chemical and geometric aspects.

A crystalline component may be in a “semicrystalline state” in that longsegments of polymer chains appear in both amorphous and crystallinestates or phases at 20° C. or above. The amorphous phase is consideredto be a randomly tangled mass of polymer chains. The X-ray diffractionpattern of an amorphous polymer is a diffuse halo indicative of noordering of the polymer structure. Amorphous polymers show softeningbehavior at the glass transition temperature, but no true melt or firstorder transition. A material in a semicrystalline state showscharacteristic melting points, above which the crystalline latticesbecome disordered and rapidly lose their identity. The X-ray diffractionpattern of such “semicrystalline” materials generally is distinguishedby either concentric rings or a symmetrical array of spots, which areindicative of the nature of the crystalline order. Thus, herein a“crystalline” component encompasses semicrystalline materials.

The crystalline component includes at least one material thatcrystallizes, preferably above room temperature (i.e., 20° C. to 25°C.). Such crystallinity, that may be provided by the aggregation ofcrystallizable moieties present in the component (e.g., when thecomponent is a polymer, in the backbone (i.e., main chain) or pendantsubstituents (i.e., side chains) of the component), can be determined bywell known crystallographic, calorimetric, or dynamic/mechanicalmethods. For the purposes of the present invention, this componentimparts to the resin system at least one melting temperature (T_(m)) asmeasured experimentally (for example by DSC) of greater than about 20°C. Preferably, this component imparts a T. to the resin system of about30° C.-100° C. If more than one crystalline material is used in thecrystalline component, more than one distinct melting point may be seen.

The number average molecular weight of the crystalline component mayvary over a broad range. Preferably, the molecular weight is less than10,000 grams per mole (g/mol), and preferably no greater than about 5000g/mol. Preferably, the molecular weight is at least about 150 g/mol, andmore preferably at least about 400 g/mol. At molecular weights less thanabout 150 the crystalline melting point may be too low. At molecularweights greater than about 10,000 the crystalline melting point may betoo high.

The crystalline monomers suitable for use in the resin system includemonomers containing urethane, ether, ester, amide, imide groups, orcombinations thereof. Preferred crystalline monomers contain reactivegroups capable of polymerizing and/or crosslinking Especially preferredare monomers with a reactive functionality greater than one.

The crystalline polymers (including oligomers) suitable for use in theresin system can have crystalline main chain (i.e., linear) or pendant(i.e., side chain) segments. Preferred materials also contain reactivegroups capable of polymerizing and/or crosslinking Especially preferredare crystalline oligomers or prepolymers with a reactive functionalityof at least two.

Examples of suitable crystalline materials having crystallizable mainchain or backbone segments include, but are not limited to, polyesters(including polycaprolactones), polyethers, polythioethers,polyarylalkylenes, polysilanes, polyamides, polyolefins (preferably,formed from lower, e.g., C₂-C₃, olefins), and polyurethanes.

Preferred crystalline materials are saturated, linear, aliphaticpolyester polyols (particularly diols) containing primary hydroxyl endgroups. Examples of commercially available materials useful as thecrystalline component in the resin systems of the invention include someresins available under the trade designation LEXOREZ from InolexChemical Co., Philadelphia, Pa. Examples of other polyester polyolsuseful in the compositions of the invention are those available underthe trade designation RUCOFLEX from Ruco Polymer Corp., Hicksville, N.Y.Examples of polycaprolactones that are useful in the invention includethose available under the trade designations TONE 0230, TONE 0240, andTONE 0260 from Dow Chemical Co., Midland, Mich. Especially preferredmaterials are saturated, linear, aliphatic polyester polyols that aremodified (e.g., through primary hydroxyl end groups) to introducepolymerizable, unsaturated functional groups, e.g., polycaprolactonediol reacted with 2-isocyanatoethyl methacrylate, methacryloyl chloride,or methacrylic anhydride.

The crystalline materials may also have a dendritic, hyperbranched, orstar-shaped structure, for example, with varying degrees of branching.Dendritic polymers are polyfunctional compounds and include any of theknown dendritic architectures including dendrimers, regular dendrons,dendrigrafts, and hyperbranched polymers. Dendritic polymers arepolymers with densely branched structures having a large number of endreactive groups. A dendritic polymer includes several layers orgenerations of repeating units which all contain one or more branchpoints. Dendritic polymers, including dendrimers and hyperbranchedpolymers, can be prepared by condensation, addition, or ionic reactionsof monomeric units having at least two different types of reactivegroups.

Dendritic polymers are comprised of a plurality of dendrons that emanatefrom a common core, which core usually comprises a group of atoms.Dendritic polymers generally consist of peripheral surface groups,interior branch junctures having branching functionalities greater thanor equal to two, and divalent connectors that covalently connectneighboring branching junctures.

Dendrons and dendrimers may be ideal or non-ideal, i.e., imperfect ordefective. Imperfections are normally a consequence of either incompletechemical reactions or unavoidable competing side reactions.

Hyperbranched polymers are dendritic polymers that contain high levelsof non-ideal irregular branching arrays as compared with the more nearlyperfect regular structure dendrimers. Specifically, hyperbranchedpolymers contain a relatively high number of irregular branching arraysin which not every repeat unit contains a branch juncture. Consequently,hyperbranched polymers may be viewed as intermediate between linearpolymers and dendrimers. Yet they are dendritic because of theirrelatively high branch-juncture content per individual macromolecule.

Star-shaped polymers typically consist of polymer chains emanating froma central core.

The preparation and characterization of dendrimers, dendrons,dendrigrafts, hyperbranched polymers, and star-shaped are well known.Examples of dendrimers and dendrons, and methods of synthesizing thesame are set forth in U.S. Pat. No. 4,507,466 (Tomalia et al.), No.4,558,120 (Tomalia et al.), No. 4,568,737 (Tomalia et al.), No.4,587,329 (Tomalia et al.), No. 4,631,337 (Tomalia et al.), No.4,694,064 (Tomalia et al.), No. 4,713,975 (Tomalia et al.), No.4,737,550 (Tomalia), No. 4,871,779 (Killat et al.), and No. 4,857,599(Tomalia et al.). Examples of hyperbranched polymers and methods ofpreparing the same are set forth, for example, in U.S. Pat. No.5,418,301 (Hult et al.). Some dendritic polymers are also commerciallyavailable. For example, 3- and 5-generation hyperbranched polyesterpolyols may be obtained from Perstorp Polyols, Inc., Toledo, Ohio.Examples of star polymers and methods of preparing the same are setforth, for example, in U.S. Pat. No. 5,830,986 (Merrill, et al.), No.5,859,148 (Borggreve, et al.), No. 5,919,870 (Letchford, et al.), andNo. 6,252,014 (Knauss).

The dendritic polymers useful in this invention may include any numberof generations, preferably three to five generations.

Generally, any of the known dendritic polymers having crystallineperipheral groups, or having peripheral groups that can be reacted withanother compound to crystalline peripheral groups are suitable for usein the resin system in the compositions of this invention. Examples ofsuitable dendritic polymers include polyethers, polyesters,polythioether, polyarylalkylenes, polysilanes, polyamides,polyurethanes, and any other condensation polymers.

Examples of suitable crystalline polymeric materials havingcrystallizable pendant moieties (i.e., side chains) include, but are notlimited to polymeric materials having the following general formula:

wherein R is hydrogen or a (C₁-C₄)alkyl group, X is —CH₂—, —C(O)O—,—O—C(O)—, —C(O)—NH—, —HN—C(O)—, —O—, —NH—, —O—C(O)—NH—, —HN—C(O)—O—,—HN—C(O)—NH—, or —Si(CH₃)₂—, m is the number of repeating units in thepolymer, and n is great enough to provide sufficient side chain lengthand conformation to form polymers containing crystalline domains orregions. Preferably, m is at least 2, and more preferably, 2 to 100, andpreferably, n is at least 10. The crystalline polymeric materials may beprepared by the polymerization of monomers containing the pendant (sidechain) crystallizable moieties or by the introduction of pendantcrystallizable moieties by chemical modification of a polyacrylate,polymethacrylate, polyacrylamide, polymethacrylamide, polyvinyl ester,or poly-α-olefin polymers or copolymers. The preparation andmorphology/conformational properties that determine the crystallinecharacter of such side chain crystallizable or “comb-like” polymers arereviewed by Plate and Shibaev, “Comb-Like Polymers. Structure andProperties,” Journal of Polymer Science, Macromolecular Reviews, 8,117-253 (1974).

Examples of suitable crystalline materials are acrylate or methacrylatepolymers derived from acrylate or methacrylate esters of nontertiaryhigher alkyl alcohols. As used herein, the term “(meth)acrylate” meansmethacrylate or acrylate. The alkyl groups of these alcohols contain atleast about 12, preferably about 16-26, carbon atoms. Examples ofcrystalline monomers that can be used to make crystalline polymericmaterials include dodecyl (meth)acrylate, isotridecyl (meth)acrylate,n-tetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-octadecyl(meth)acrylate, behenyl (meth)acrylate, eicosanyl (meth)acrylate, andmixtures thereof. Hexadecyl (methacrylates) and octadecyl(meth)acrylates are commercially available from Monomer-Polymer & DajacLaboratories, Inc., Feasterville, Pa., and Polysciences, Inc.,Warrington, Pa. (Meth)acrylate esters of non-tertiary alcohols, thealkyl portions of which comprise from about 30 to about 50 carbon atoms,are commercially available under the trade designation UNILIN fromPetrolite Corp., Tulsa, Okla. As long as the crystalline oligomer orpolymer has a melting point, it can include noncrystallizable monomers.Acrylate or methacrylate or other vinyl monomers that are free-radicallyreactive may optionally be utilized in conjunction with one or more ofthe side chain crystallizable acrylate and methacrylate monomersprovided that the resultant polymer has a melting or softeningtemperature above room temperature. Examples of such free-radicallyreactive monomers include, but are not limited to, tert-butyl acrylate,isobornyl acrylate, butyl methacrylate, vinyl acetate, acrylonitrile,styrene, isooctyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, andthe like. Various combinations of these monomers can be used.

Also suitable are side chain crystalline polymeric materials derivedfrom higher α-olefin monomers, such as poly-1-decene, poly-1-dodecene,poly-l-tetradecene, and poly-1-hexadecene, and higher vinyl esters, suchas vinyl tetradecanoate, vinyl hexadecanoate and vinyl octadecanoate.

Additional side chain crystalline polymeric materials for use in thepresent invention include polymers with pendant polymerizable groups.The pendant polymerizable groups may be introduced by the incorporationof functional monomers in the side chain crystalline polymer.

Useful functional monomers include those unsaturated aliphatic,cycloaliphatic, and aromatic compounds having up to about 36 carbonatoms that include a functional group capable of further reaction, suchas a hydroxyl, amino, azlactone, oxazolinyl, 3-oxobutanoyl (i.e.,acetoacetyl), carboxyl, isocyanato, epoxy, aziridinyl, acyl halide,vinyloxy, or anhydride group.

Also suitable are functional monomers having the general formula:

wherein R¹ is hydrogen, a (C₁ to C₄)alkyl group, or a phenyl group,preferably hydrogen or a methyl group; R² is a single bond or a divalentlinking group that joins an ethylenically unsaturated group tofunctional group A and preferably contains up to 34, more preferably upto 18, most preferably up to 10 carbon atoms, and, optionally, oxygenand nitrogen atoms and, when R² is not a single bond, is preferablyselected from

in which R³ is an alkylene group having 1 to 6 carbon atoms, a 5- or6-membered cycloalkylene group having 5 to 10 carbon atoms, or analkylene-oxyalkylene in which each alkylene includes 1 to 6 carbon atomsor is a divalent aromatic group having 6 to 16 carbon atoms; and A is afunctional group, capable of reaction with a co-reactive functionalgroup (which is part of an unsaturated monomer) to form a covalent bond,preferably selected from the class consisting of hydroxyl, amino(especially secondary amino), carboxyl, isocyanato, aziridinyl, epoxy,acyl halide, vinyloxy, azlactone, oxazolinyl, acetoacetyl, and anhydridegroups.

Representative hydroxyl group-substituted functional monomers includethe hydroxyalkyl (meth)acrylates and hydroxyalkyl (meth)acrylamides suchas 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,3-chloro-2-hydroxypropylmethyl (meth)acrylate, 2-hydroxyethyl(meth)acrylamide, 4-hydroxycyclohexyl (meth)acrylate,3-acryloyloxyphenol, 2-(4-acryloyloxyphenyl)-2-(4-hydroxyphenyl)propane(also called bisphenol A monoacrylate), 2-propyn-1-ol, and 3-butyn-1-ol.

Representative amino group-substituted functional monomers include2-methyl aminoethyl methacrylate, 3-aminopropyl methacrylate,4-aminocyclohexyl methacrylate, N-(3-aminophenyl)acrylamide,4-aminostyrene, N-acryloylethylenediamine, and4-aminophenyl-4-acrylamidophenylsulfone.

Representative azlactone group-substituted functional monomers include2-ethenyl-1,3-oxazolin-5-one; 2-ethenyl-4-methyl-1,3-oxazolin-5-one;2-isopropenyl-1,3-oxazolin-5-one;2-isopropenyl-4-methyl-1,3-oxazolin-5-one;2-ethenyl-4,4-dimethyl-1,3-oxazolin-5-one;2-isopropenyl-4,4-dimethyl-1,3-oxazolin-5-one;2-ethenyl-4-methyl-4-ethyl-1,3-oxazolin-5-one;2-isopropenyl-3-oxa-1-aza[4.5]spirodec-1-ene-4-one;2-ethenyl-5,6-dihydro-4H-1,3-oxazin-6-one;2-ethenyl-4,5,6,7-tetrahydro-1,3-oxazepin-7-one;2-isopropenyl-5,6-dihydro-5,5-di(2-methylphenyl)-4H-1,3-oxazin-6-one;2-acryloyloxy-1,3-oxazolin-5-one;2-(2-acryloyloxy)ethyl-4,4-dimethyl-1,3-oxazolin-5-one;2-ethenyl-4,5-dihydro-6H-1,3-oxazin-6-one, and2-ethenyl-4,5-dihydro-4,4-dimethyl-6H-1,3-oxazin-6-one.

Representative oxazolinyl group-substituted functional monomers include2-vinyl-2-oxazoline, 2-isopropenyl-2-oxazoline,2-(5-hexenyl)-2-oxazoline, 2-acryloxy-2-oxazoline,2-(4-acryloxyphenyl)-2-oxazoline, and 2-methacryloxy-2-oxazoline.

Representative acetoacetyl group-substituted functional monomers include2-(acetoacetoxy)ethyl (meth)acrylate, styryl acetoacetate, isopropenylacetoacetate, and hex-5-enyl acetoacetate.

Representative carboxyl group-substituted functional monomers include(meth)acrylic acid, 3-(meth)acryloyloxy-propionic acid,4-(meth)acryloyloxy-butyric acid, 2-(meth)acryloyloxy-benzoic acid,3-(meth)acryloyloxy-5-methyl benzoic acid,4-(meth)acryloyloxymethyl-benzoic acid, phthalic acidmono-(2-(meth)acryloyloxy-ethyl) ester, 2-butynoic acid, and 4-pentynoicacid.

Representative isocyanate group-substituted functional monomers include2-isocyanatoethyl (meth)acrylate, 3-isopropenyl dimethyl benzylisocyanate, 3-isocyanatopropyl (meth)acrylate, 4-isocyanatocyclohexyl(meth)acrylate, 4-isocyanatostyrene, 2-methyl-2-propenoyl isocyanate,4-(2-acryloyloxyethoxycarbonylamino)phenylisocyanate, allyl2-isocyanatoethylether, and 3-isocyanato-1-propene.

Representative epoxy group-substituted functional monomers includeglycidyl (meth)acrylate, thioglycidyl (meth)acrylate,3-(2,3-epoxypropoxy)phenyl (meth)acrylate,2-[4-(2,3-epoxypropoxy)phenyl]-2-(4-acryloyloxy-phenyl)propane,4-(2,3-epoxypropoxy)cyclohexyl (meth)acrylate, 2,3-epoxycyclohexyl(meth)acrylate, and 3,4-epoxycyclohexyl (meth)acrylate.

Representative aziridinyl group-substituted functional monomers includeN-(meth)acryloylaziridine, 2-(1-aziridinyl)ethyl (meth)acrylate,4-(1-aziridinyl)butyl (meth)acrylate, 2-(2-(1-aziridinyl)ethoxy)ethyl(meth)acrylate, 2-(2-(1-aziridinyl)ethoxycarbonylamino)ethyl(meth)acrylate,12-(2-(2,2,3,3-tetramethyl-1-aziridinyl)ethoxycarbonylamino)dodecyl(meth)acrylate, and 1-(2-propenyl)aziridine.

Representative acyl halide group-substituted functional monomers include(meth)acryloyl chloride, a-chloroacryloyl chloride, acryloyloxyacetylchloride, 5-hexenoyl chloride, 2-(acryloyloxy) propionyl chloride,3-(acryloylthioxy) propionyl chloride, and 3-(N-acryloyl-N-methylamino)propionyl chloride.

Representative vinyloxy group-substituted functional monomers include2-(ethenyloxy)ethyl (meth)acrylate, 3-(ethynyloxy)-1-propene,4-(ethynyloxy)-1-butene, and4-(ethenyloxy)butyl-2-acrylamido-2,2-dimethylacetate. Representativeanhydride group-substituted functional monomers include maleicanhydride, acrylic anhydride, itaconic anhydride, 3-acryloyloxyphthalicanhydride, and 2-methacryloxycyclohexanedicarboxylic acid anhydride.

Starting from the functional main chain (i.e., linear) or pendant (i.e.,side chain) crystalline oligomers or polymer segments, the introductionof polymerizable groups preferably takes place by reaction with suitableunsaturated compounds, in particular (meth)acrylic, allyl, or vinylcompounds, according to known methods of organic chemistry.Polymerizable methacrylate groups can be introduced, for example, byesterification of alcohol groups on the polymer with methacrylic acid orby acylation with methacrylic acid chloride or methacrylic acidanhydride. Furthermore, the reaction of alcohol groups on thecrystalline polymer with 2-isocyanatoethyl methacrylate (IEM) isparticularly suitable.

Analogously, the functionalized crystalline starting materials can bemodified with other unsaturated polymerizable groups, such as acrylic,vinyl, allyl, vinyl ether, or styryl in place of methacrylic groups.Suitable reagents are acrylic acid, acrylic acid chloride, vinyl aceticacid, and 4-vinyl benzoic acid. Preferred polymerizable groups aremethacrylate and acrylate groups.

Another crystalline component includes compounds of the formula:

wherein each Q independently includes polyester segments, polyamidesegments, polyurethane segments, polyether segments, or combinationsthereof. Preferably, each Q independently includes poly(caprolactone)segments. More preferably, such crystalline compounds includepolymerizable groups, such as epoxy, acid, alcohol, and ethylenicallyunsaturated reactive sites. Particularly preferred such materialsinclude unsaturated polymerizable groups, such as methacrylic, acrylic,vinyl, and styryl groups.

Filler System

Fillers for use in the filler system may be selected from a wide varietyof conventional fillers for incorporation into resin systems.Preferably, the filler system includes one or more conventionalmaterials suitable for incorporation in compositions used for medicalapplications, for example, fillers currently used in dental restorativecompositions. Thus, the filler systems used in the compositions of thepresent invention are incorporated into the resin systems, andparticularly mixed with the crystalline component of the resin system.

Fillers may be either particulate or fibrous in nature. Particulatefillers may generally be defined as having a length to width ratio, oraspect ratio, of 20:1 or less, and more commonly 10:1 or less. Fiberscan be defined as having aspect ratios greater than 20:1, or morecommonly greater than 100:1. The shape of the particles can vary,ranging from spherical to ellipsoidal, or more planar such as flakes ordiscs. The macroscopic properties can be highly dependent on the shapeof the filler particles, in particular the uniformity of the shape.

Preferred particulate filler is finely divided and has an averageparticle size (preferably, diameter) of less than about 10 micrometers(i.e., microns). Preferred micron-size particulate filler has an averageparticle size of at least about 0.2 microns up to 1 micrometers.Nanoscopic particles have an average primary particle size of less than200 nm (0.2 microns). The filler can have a unimodal or polymodal (e.g.,bimodal) particle size distribution.

Micron-size particles are very effective for improving post-cure wearproperties. In contrast, nanoscopic fillers are commonly used asviscosity and thixotropy modifiers. Due to their small size, highsurface area, and associated hydrogen bonding, these materials are knownto assemble into aggregated networks. Materials of this type(“nanoscopic” materials) have average primary particle sizes (i.e., thelargest dimension, e.g., diameter, of unaggregated material) of lessthan 200 nanometers (nm). Preferably, the nanoscopic particulatematerial has an average primary particle size of at least about 2nanometers (nm), and preferably at least about 7 nm. Preferably, thenanoscopic particulate material has an average primary particle size ofno greater than about 50 nm, and more preferably no greater than about20 nm in size. The average surface area of such a filler is preferablyat least about 20 square meters per gram (m²/g), more preferably, atleast about 50 m²/g, and most preferably, at least about 100 m²/g.

The filler can be an inorganic material. It can also be a crosslinkedorganic material that is insoluble in the polymerizable resin, and isoptionally filled with inorganic filler. The filler is preferablygenerally non-toxic and suitable for use in the mouth. The filler can beradiopaque, radiolucent, or nonradiopaque. Fillers as used in dentalapplications are typically ceramic in nature.

Examples of suitable inorganic fillers are naturally occurring orsynthetic materials such as quartz, nitrides (e.g., silicon nitride),glasses derived from, for example Ce, Sb, Sn, Zr, Sr, Ba, or Al,colloidal silica, feldspar, borosilicate glass, kaolin, talc, titania,and zinc glass, zirconia-silica fillers; and low Mohs hardness fillerssuch as those described in U.S. Pat. No. 4,695,251 (Randklev).

Examples of suitable organic filler particles include filled or unfilledpulverized polycarbonates, polyepoxides, and the like. Preferred fillerparticles are quartz, submicron silica, and non-vitreous microparticlesof the type described in U.S. Pat. No. 4,503,169 (Randklev). Mixtures ofthese fillers can also be used, as well as combination fillers made fromorganic and inorganic materials.

Optionally, the surface of the filler particles may be treated with asurface treatment, such as a silane-coupling agent, in order to enhancethe bond between the filler and the resin system. The coupling agent maybe functionalized with reactive curing groups, such as acrylates,methacrylates, and the like.

The filler particles used to impart a noncovalent structure can becomposed of silica, alumina, zirconia, titania, or mixtures of thesematerials with each other or with carbon. In their synthesized state,these materials are commonly hydrophilic, due to the presence of surfacehydroxyl groups. However, the materials may also be modified bytreatment with appropriate agents, such as alkyl silanes, in order tomodify this character. For example, the surface of a filler particle maybe rendered neutral, hydrophobic, or reactive, depending on the desiredproperties. Fumed silica is a preferred compound for impartingself-supporting character, due to its low cost, commercial availability,and wide range of available surface character.

Preferably, the total amount of filler system is greater than 50 wt-%,more preferably, greater than 60 wt-%, and most preferably, greater than70 wt-%, based on the total weight of the composition. If the fillersystem includes fibers, the fibers are present in an amount of less than20 wt-%, based on the total weight of the composition. Preferably, thetotal amount of filler system is no more than about 95 wt-%, and morepreferably, no more than about 80 wt-%, based on the total weight of thecomposition. Significantly, such high filler loadings with the resinsystems of the present invention is unexpected, particularly inproviding a malleable composition.

Initiator System

The compositions of the present invention also contain an initiatorsystem, i.e., one initiator or a mixture of two or more initiators,which are suitable for hardening (e.g., polymerizing and/orcrosslinking) of the resin system. The initiators are preferably freeradical initiators, which may be activated in a variety of ways, e.g.,heat and/or radiation. Thus, for example, the initiator system can be athermal initiator system (e.g., azo compounds and peroxides), or aphotoinitiator system. Preferably, the initiator system includes one ormore photoinitiators. More preferably, the initiator system includes atleast one photoinitiator active in the spectral region of about 300nanometers (nm) to about 1200 nm and capable of promoting free radicalpolymerization and/or crosslinking of ethylenically unsaturated moietiesupon exposure to light of suitable wavelength and intensity. A widevariety of such photoinitiators can be used. The photoinitiatorpreferably is soluble in the resin system. Preferably, they aresufficiently shelf stable and free of undesirable coloration to permitstorage and use under typical dental operatory and laboratoryconditions. Visible light photoinitiators are preferred. One type ofsuitable initiator (i.e., initiator system) is described in U.S. Pat.No. 5,545,676 (Palazzotto et al.), which includes a three component orternary photoinitiator system. This system includes an iodonium salt,e.g., a diaryliodonium salt, which can be a simple salt (e.g.,containing an anion such as Cl⁻, Br⁻, I⁻, or C₂H₅SO₃ ⁻) or a metalcomplex salt (e.g., containing SbF₅OH⁻ or AsF₆ ⁻). Mixtures of iodoniumsalts can be used if desired. The second component in this ternaryphotoinitiator system is a sensitizer, which is capable of lightabsorption within the range of wavelengths of about 400 nm to about 1200nm. The third component in this ternary photoinitiator system is anelectron donor and includes amines (including aminoaldehydes andaminosilanes or other amines as described for the first initiatorsystem), amides (including phosphoramides), ethers (includingthioethers), ureas (including thioureas), ferrocene, sulfinic acids andtheir salts, salts of ferrocyanide, ascorbic acid and its salts,dithiocarbamic acid and its salts, salts of xanthates, salts of ethylenediamine tetraacetic acid and salts of tetraphenylboronic acid.

Examples of sensitizers suitable for use in a ternary photoinitiatorsystem include ketones, coumarin dyes (e.g., ketocoumarins), xanthenedyes, acridine dyes, thiazole dyes, thiazine dyes, oxazine dyes, azinedyes, aminoketone dyes, porphyrins, aromatic polycyclic hydrocarbons,p-substituted aminostyryl ketone compounds, aminotriaryl methanes,merocyanines, squarylium dyes, and pyridinium dyes. Ketones (e.g.,monoketones or alpha-diketones), ketocoumarins, aminoarylketones, andp-substituted aminostyryl ketone compounds are preferred sensitizers.Examples of particularly preferred visible light sensitizers includecamphorquinone, glyoxal, biacetyl, 3,3,6,6-tetramethylcyclohexanedione,3,3,7,7-tetramethyl-1.2-cycloheptanedione,3,3,8,8-tetramethyl-1,2-cyclooctanedione,3,3,18,18-tetramethyl-1,2-cyclooctadecanedione, dipivaloyl, benzil,furil, hydroxybenzil, 2,3-butanedione, 2,3-pentanedione,2,3-hexanedione, 3,4-hexanedione, 2,3-heptanedione, 3,4-heptanedione,2,3-octanedione, 4,5-octanedione, and 1,2-cyclohexanedione. Of these,camphorquinone is the most preferred sensitizer.

Yet another type of photoinitiator includes acylphosphine oxides, suchas those described in European Pat. Application No. 173567 (Ying).Suitable acylphosphine oxides are preferably of the general formula(R⁴)₂—P(═O)—C(═O)—R⁵, wherein each R⁴ is individually a hydrocarbongroup, preferably an alkyl group, alicyclic group, aryl group, andaralkyl group, any of which can be substituted with a halo-, alkyl- oralkoxy-group, or the two R⁴ groups can be joined to form a ring alongwith the phosphorous atom, and wherein R⁵ is a hydrocarbon group,preferably, a S—, O—, or N-containing five- or six-membered heterocyclicgroup, or a —Z—C(═O)—P(═O)—(R⁴)₂ group, wherein Z represents a divalenthydrocarbon group such as alkylene or phenylene having from 2 to 6carbon atoms. Examples of suitable acylphosphine oxides includebis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide, for example.Optionally, tertiary amine reducing agents may be used in combinationwith an acylphosphine oxide. Illustrative tertiary amines useful in theinvention include those described above as well as ethyl4-(N,N-dimethylamino)benzoate and N,N-dimethylaminoethyl methacrylate.

Mono- and di-ketones can also be used as photoinitiators. Examples ofsuch systems are described in U.S. Pat. No. 4,071,424 (Dart et al.).

Still another class of photoinitiators includes ionic dye-counterioncomplex initiators that include a borate anion and a complementarycationic dye. Borate anions useful in these photoinitiators generallycan be of the formula B(R⁶)₄ ⁻ wherein each R⁶ is independently analkyl, aryl, alkaryl, allyl, aralkyl, alkenyl, alkynyl, alicyclic, andsaturated or unsaturated heterocyclic groups. Cationic counterions canbe cationic dyes, quaternary ammonium groups, transition metalcoordination complexes, and the like. Cationic dyes useful ascounterions can be cationic methine, polymethine, triarylmethine,indoline, thiazine, xanthene, oxazine or acridine dyes. Quaternaryammonium groups useful as counterions can be trimethylcetylammonium,cetylpyridinium, and tetramethylammonium. Other organophilic cations caninclude pyridinium, phosphonium, and sulfonium. Cationic transitionmetal coordination complexes that may be useful as counterions can becomplexes of cobalt, ruthenium, osmium, zinc, iron, and iridium withligands such as pyridine, 2,2′-bipyridine,4,4′-dimethyl-2,2′-bipyridine, 1,10-phenanthroline,3,4,7,8-tetramethylphenanthroline, 2,4,6-tri(2-pyridyl-s-triazine) andrelated ligands. Borate salt photoinitiators are described, for example,in U.S. Pat. No. 4,772,530 (Gottschalk et al.), No. 4,954,414 (Adair etal.), No. 4,874,450 (Gottschalk), No. 5,055,372 (Shanklin et al.), andNo. 5,057,393 (Shanklin et al.).

Preferred visible light-induced initiators include camphorquinonecombined with a suitable hydrogen donor (e.g., an amine such as thosedescribed above for the first initiator system), and optionally adiaryliodonium simple or metal complex salt, chromophore-substitutedhalomethyl-s-triazine, or halomethyl oxadiazole. Particularly preferredvisible light-induced photoinitiators include combinations of analpha-diketone, e.g., camphorquinone with additional hydrogen donors,and optionally a diaryliodonium salt, e.g., diphenyliodonium chloride,bromide, iodide or hexafluorophosphate.

Preferred ultraviolet light-induced polymerization initiators includeketones, such as benzyl and benzoin, acyloins, and acyloin ethers.Preferred ultraviolet light-induced polymerization initiators include2,2-dimethoxy-2-phenylacetophenone available under the trade designationIRGACURE 651 and benzoin methyl ether (2-methoxy-2-phenylacetophenone),both from Ciba Speciality Chemicals Corp., Tarrytown, N.Y.

The initiator system is present in an amount sufficient to provide thedesired rate of hardening (e.g., polymerizing and/or crosslinking) For aphotoinitiator, this amount will be dependent in part on the lightsource, the thickness of the layer to be exposed to radiant energy, andthe extinction coefficient of the photoinitiator. Preferably, theinitiator system is present in a total amount of at least about 0.01wt-%, more preferably, at least about 0.03 wt-%, and most preferably, atleast about 0.05 wt-%, based on the weight of the composition.Preferably, the initiator system is present in a total amount of no morethan about 10 wt-%, more preferably, no more than about 5 wt-%, and mostpreferably, no more than about 2.5 wt-%, based on the weight of thecomposition.

Surfactant System

The compositions of the invention may contain a surfactant system, i.e.,one surfactant or a mixture of two or more surfactants. Thesesurfactants, when used in small amounts may interact with othercomponents of the composition, such as an inorganic filler material, toenhance the formation of a noncovalent three-dimensional structure. Suchsurfactants can be nonionic, anionic, or cationic. The surfactant(s) canbe copolymerizable with the resin system or non-copolymerizable. Aconsideration in the choice of a surfactant that can be used is thedegree to which the ingredients of the system are able to participate inhydrogen bonding.

Preferably, the total amount of surfactant system is at least about 0.05wt-%, more preferably, at least about 0.1 wt-%, and most preferably, atleast about 0.2 wt-%, based on the total weight of the composition.Preferably, the total amount of surfactant system is no more than about5.0 wt-%, more preferably, no more than about 2.5 wt-%, and mostpreferably, no more than about 1.5 wt-%, based on the total weight ofthe composition.

Typical nonionic surfactants are usually condensation products of anorganic aliphatic or alkylaromatic hydrophobic compound and an alkyleneoxide, such as ethylene oxide, which is hydrophilic. The length of theethylene oxide chain of the condensation product as well as the lengthof the starting hydrocarbon compound can be adjusted to achieve thedesired balance between the hydrophobic and hydrophilic elements.Examples of such surfactants include nonylphenoxypoly (ethyleneoxy)ethanols available under the trade designation IGEPAL CO fromRhone-Poulenc, Cranbury, N.J., and nonylphenyl polyethylene glycolethers available under the trade designation TERGITOL NP from DowChemical Co., Midland, Mich.

Other nonionic surfactants include, but are not limited to, sorbitanfatty acid esters available under the trade designation SPAN from ICI,Runcorn Cheshire, UK, and polyoxyethylene sorbitan fatty acid estersavailable under the trade designation TWEEN from ICI. Still othersatisfactory nonionic surfactants include, but are not limited to, shortchain polyfunctional molecules like glycerine, ethylene diamine,ethylene glycol, propylene glycol; and long chain polyfunctionalmolecules like polyalkylene glycols available under the tradedesignation UCON from Dow Chemical, polyoxyethylene sorbitol availableunder the trade designation ATLAS G-2240 from ICI, polyethylene glycolsand their methyl ethers available under the trade designation CARBOWAXfrom Dow Chemical.

Typical cationic surfactants include, but are not limited to, quaternaryammonium salts in which at least one higher molecular weight group andtwo or three lower molecular weight groups are linked to a commonnitrogen atom to produce a cation, and wherein theelectrically-balancing anion is selected from the group consisting of ahalide (e.g., bromide or chloride), acetate, nitrite, and loweralkosulfate (e.g., methosulfate). The higher molecular weightsubstituent(s) on the nitrogen is/are often (a) higher alkyl group(s),containing at least about 10 carbon atoms, and the lower molecularweight substituents may be lower alkyl of about 1 to about 4 carbonatoms which may be substituted with hydroxy. One or more of thesubstituents may include an aryl moiety or may be replaced by an arylmoiety, such as benzyl or phenyl. Among the possible lower molecularweight substituents are also lower alkyls of about 1 to about 4 carbonatoms substituted by lower polyalkoxy moieties such as polyoxyethylenemoieties bearing a hydroxyl end group. Examples of useful quaternaryammonium halide surfactants for use in the present invention include,but are not limited to, bis(hydrogenated tallowalkyl) dimethylquaternary ammonium chloride available under the trade designationARQUAD 2HT-75 from Akzo Nobel, McCook, Ill., dimethyl di(cocoalkyl)quaternary ammonium chloride available under the trade designationARQUAD 2C-75 from Akzo Nobel, and N-(tallowalkyl)-1,3-propanediaminedioleate available under the trade designation DUOMEEN TDO from AkzoNobel.

Typical anionic surfactants include, but are not limited to, dihexylsodium sulfosuccinate available under the trade designation AEROSOL MAfrom BASF, Ludwigshafen, Germany, dioctyl sodium sulfosuccinateavailable under the trade designation ALROWET D-65 from Ciba SpecialityChemicals, the sodium salt of a polymerized carboxylic acid availableunder the trade designations DAXAD 30 from W. R. Grace, Columbia, Md.,TAMOL 731 from Rohm and Haas, Philadelphia, Pa., sodium alkylnaphthalenesulfonate available under the trade designation NEKAL BA-75 from Rohmand Haas, as well as sodium oleate, sodium stearate, sulfated castoroil, zinc hydroxy stearate, all of which are available from a variety ofsuppliers.

Optional Additives

The composition may additionally include optional agents such ascolorants (e.g., pigments conventionally used for shade adjustment),flavorants, medicaments, stabilizers (such as BHT), viscosity modifiers,and the like. Such agents may optionally include reactive functionalityso that they will be copolymerized with the resin.

Methods of Use and Products

The compositions of the present invention can be shaped (e.g., molded)into a variety of forms like three-dimensional shapes, preformed sheets,arch-shaped trays, ropes, buttons, woven, or non-woven webs, and thelike. The composition can be shaped (to form a first shape) in a varietyof ways including, for example, extruding, injection molding,compression molding, thermoforming, vacuum forming, pressing,calendering, and web processing using rollers. Typically, asemi-finished shape is formed using a mold with a positive and negativeimpression.

The shaped articles can be sold individually or in multiple units,preferably packaged in a way that protects them from heat and/or lightthat can activate the initiator system contained in the composition.

Generally, a preformed article of appropriate size and shape (the firstshape) is selected and custom shaped at a temperature of about 15° C. to38° C. (preferably, about 20° C. to 38° C., which encompasses typicalroom temperatures and body temperatures, and more preferably, at roomtemperature). This shaping can be done by a variety of methods includingapplying pressure with fingers or an instrument of choice (e.g., handoperation of dental composite instrument), trimming, cutting, sculpting,grinding, etc. Once the desired custom shape has been achieved, thearticle is hardened (e.g., cured) by exposing it to heat/radiation tocause activation of the initiator system. This can be done either in asingle step, or in multiple steps with successive steps of customshaping being done in-between. One or more of these steps can be carriedout in an oxygen-free inert atmosphere or in vacuum. After the finalshaping and hardening steps, the hardened article can be furthermodified in shape by grinding, trimming, etc., if desired. Once thefinal custom shape of the article has been obtained, it can be polished,painted, or otherwise surface treated, if required for the intendedapplication. Preferably, the final custom shaped articles prepared fromthe compositions of the present invention do not need an additionalveneering material (e.g., a second material that provides a desiredappearance or property). The intended application may require mounting,bonding, or otherwise attaching the custom shaped cured article to asecond object adhesively, mechanically, or by combination of both.

For the preparation of a provisional dental crown, an appropriate shapeand size of a preformed crown is selected and the preformed crown isseated on the prepared tooth to determine the extent of trimming andshaping required, optionally making marks on the crown. The preformedcrown is removed from the mouth, the required shape and size adjustmentsare made by cutting, trimming, shaping, etc., and then re-seated on thetooth preparation where additional shape adjustments are made to provideoptimum custom fit, including gingival, lateral, and occlusal fit. Thepreformed and reshaped crown can then be hardened, typically by exposingit to a dental curing light for a few seconds, if desired, while in themouth, and then removing it carefully from the mouth and exposing it forfinal cure to a curing light in a cure chamber, optionally incombination with heat. Alternatively, the crown can also be completelycured in the mouth by irradiating it with a dental curing light. Finaladjustments are made by grinding, trimming, etc., if required, and thefinished crown is polished and cleaned. The finished crown can then becemented as is or lined with a suitable resin material prior toplacement in the mouth.

This invention also includes a customizable dental impression tray,formed from a self-supporting composition as described herein. Dentaltrays are commonly used to obtain accurate impressions of a patient'steeth. Commonly, the tray is supplied as a preformed non-customizableitem, albeit in a range of sizes. This tray is filled with an impressionmaterial (e.g., one or more flowable elastomeric materials, such aspolyvinylsiloxane, polyether, or polysulfide) and pressed around theteeth of the upper or lower jaw. The impression material containedwithin the tray is then cured in place. More accurate impressions can beobtained with increased patient comfort through the use of a customizedtray, which can be shaped to fit the patient's mouth more accuratelythan a generic “one size fits all” tray. Thus, the compositions of thepresent invention can be used to make a customizable dental impressiontray.

One of the major requirements for a dental impression tray is that theimpression material adheres to the interior surface of the tray. Due totheir shape, a mechanical interlock is typically formed between theteeth and the impression material during curing. Although the impressionmaterial may be flexible even after curing, insufficient adhesion willcause the impression material to separate from the tray or tear duringremoval from the mouth. Current tray technology relies on addition of anadhesive to the tray prior to filling it with impression material inorder to create this bond. The present invention allows for this,although a dental impression tray can include at least one structuredsurface (i.e., a surface having a 3-dimensional structure formed fromdepressions, holes, protuberances, or the like), which can be amicroreplicated surface or be formed by a porous substrate, for example.Such a structured surface provides a mechanical interlock between thesurface of the tray and the cured impression material, analogous to thatformed between the impression material and the teeth. However, theinterlock between the tray and impression material is much moreextensive, and thus stronger than the impression material/toothinterface. As such, the requirement for an adhesive is eliminated. Thisstructured surface in the tray may be created in a number of ways,including, but not limited to, molding, embossing, or lamination of asecond structured layer such as a porous substrate (e.g., includingfilms, foams, and knit, woven, and nonwoven fabrics). If a second layeris laminated to the base material, said lamination can also contributein other ways, e.g., through enhancement of mechanical properties.

The hardenable, self-supporting structures (e.g., dental products) ofthis invention can be prepackaged either individually or as an ensemble.Such packaging material should protect these products from conditionsthat would activate the initiator system and thus cause prematurehardening, e.g., such as could result from exposure to light in the caseof a photoinitiator. In addition, the packaging material optionallyconforms to the surfaces of the product, thereby providing additionalmechanical strength in order to resist damage during shipping. Forexample, a preformed crown or tray could be packaged in a layer ofpolyethylene on all sides. The polyethylene provides a mechanicalstructure and can be sealed to avoid contact with water. If thepolyethylene were filled with an appropriate dye, e.g., carbon black,incident light would be absorbed before it could reach the enclosedproduct. If such a packaging layer is somewhat rigid, and if thepackaging material is shaped similar to the preformed article of theinvention, then the packaging could enhance the dimensional stability ofthe preformed product during shipment and storage. In certain cases, thepackaging may thus form an integral part of the product system.

The invention is also useful in a number of preformed orthodonticapplications. For example, the hardenable composition may be fabricatedinto a custom appliance such as a lingual retainer, a space retainer, ahook, a button, or a splint. As another example, the composition may beused to make a portion of an appliance, such as a custom base for anorthodontic bracket that is adapted to closely fit the curvature of apatient's tooth, or an orthodontic bracket with tiewings that areoriented at a particular angle to avoid contact with adjacent structurein the oral cavity. The composition also may be used to make a toothfacsimile that is bonded to an archwire to hide open spaces betweenteeth during the course of treatment. Furthermore, the composition maybe used to bond groups of adjacent teeth together to establish stronganchorage for other orthodontic appliances. Additionally, thecomposition may be formed into a droplet of material that is bonded toan archwire at a certain location to prevent sliding movement of thearchwire or to prevent movement of another appliance. When used inorthodontic applications, the composition of the invention can be shapedto a desired configuration in vivo and then hardened in place in theoral cavity. Alternatively, the composition can be shaped to a desiredconfiguration outside of the oral cavity using, if desired, a model ofthe patient's tooth structure. When the composition is shaped outside ofthe oral cavity, the composition is preferably hardened before placementin the oral cavity.

EXAMPLES

The following examples are given to illustrate, but not limit, the scopeof this invention. Unless otherwise indicated, all parts and percentagesare by weight and all molecular weights are weight average molecularweight.

Test Methods

Pre-Cure Elastic and Viscous Moduli (Rheology) Test

Elastic Moduli (G′) and Viscous Moduli (G″) as an indication ofcomposition rheology were measured according to the following testprocedure. A composition sample was heated to 70° C. in an oven andpressed between two Teflon-lined glass plates into a sheet having athickness of approximately 2 millimeters (mm). After cooling to roomtemperature and aging for 48 hours, an 8-mm diameter disk was cut fromthe resulting sheet. Rheological measurements were carried out on aRheometrics RDA II dynamic mechanical analyzer (Rheometric Scientific,Piscataway, N.J.) using 8-mm parallel plate fixtures. Elastic andViscous Moduli were measured at 25° C. as a function of frequency (Hz)for the disk of pre-cured composite and results reported in kilopascals(kPa).

Pre-Cure Crown Formation Test

The objective of this test is to determine if a composition could bemade into a self-supporting crown and then determine qualitatively ifthat crown is malleable, shapeable, and trimable at room temperature. Acomposite sample was manually formed into a 2-mm thick “cup”approximately the size of a molar and was pressed at 85° C. between apositive mold of a slightly reduced maxillary central incisor and anegative mold of 3M ESPE polycarbonate crown #10. The positive andnegative molds were prepared from 3M ESPE IMPRINT II Monophase and 3MESPE EXPRESS STD Putty Material (3M Co., St. Paul, Minn.), respectively.In order for a composition sample to “pass” this Test Method, thepressed crown should easily be removed from the mold after cooling toroom temperature without any markable deformation.

The crown sample was further evaluated based on its ability to be customfitted on a more heavily reduced maxillary central incisor on a TYPODONTarch (Columbia Dentoform, Long Island City, N.Y.). The crown sample wasexamined for (1) how well it retained its form while being handled, (2)how easily it could be trimmed with scissors, and (3) how well it couldbe custom-fitted on the central incisor by adapting the crown shape witha composite instrument while positioned on the reduced tooth, withouteither breaking or demonstrating any elastic deformation. In order for acomposition to “pass” this Test Method, the formed crown sample wasrequired to successfully meet each of these three quality parameters.

Pre-Cure Composite Packability Test

The packability of a composite material was qualitatively determinedaccording to the following procedure. The first molar tooth on a lowerarch model (SM-PVR-860 from Columbia Dentoform Corporation, Long IslandCity, N.Y.) was prepared with a mesio occluso cavity preparation. Ametal matrix band (dead soft HO Band-Young, type universal #1 from HenrySchein catalog) was fitted around the molar with the help of aTofflemire matrix retainer (type universal, from Henry Schein catalog).This model was then placed in a small heating chamber, which was kept ata constant temperature of 38° C. Once the model had reached atemperature of 38° C. it was taken out of the heated chamber and apellet of the composite to be tested was placed in the prepared toothcavity. Packability of the composite was evaluated by compacting thepellet in the cavity with a double-ended amalgam plugger (1/2 Black DEfrom Henry Schein catalog). The ability of the composite material to becondensed, rather than flowing around the plugging instrument, wasdetermined. Evaluation also included the ability of the compositematerial to transfer some of the compacting force to the metal matrixband, and thereby to deform the band. A composite material that bothcould be condensed in the cavity and that deformed the band was judgedto be packable.

Pre-Cure Differential Scanning Calorimetry (DSC) Test

The crystallinity and melting point of samples was determined bydifferential scanning calorimetry using a DSC 2920 instrument from TAInstruments (New Castle, Del.). A sample weighing 5-10 mg that had beenaged for at least 72 hours was placed in a standard aluminum pan andheated at 5° C./min from −40° C. to 120° C. The resulting thermogram wasexamined for evidence of a melting point range and endothermic peaksthat would be associated with the melting of crystalline species. Theabsence of endothermic peaks would be indicative of no crystallinecomponent in the sample.

Post-Cure Flexural Strength (FS) and Flexural Modulus (FM) Test

Flexural Strength and Flexural Modulus were measured according to thefollowing test procedure. A composition sample was pressed at 65° C. ina preheated mold to form a 2-mm×2-mm×25-mm test bar. The bar was aged atroom temperature for 24 hours and light cured for 90 seconds by exposureto two oppositely disposed VISILUX Model 2500 blue light guns (3M Co.).The bar was then post-cured for 180 seconds in a Dentacolor XS unit(Kulzer, Inc., Germany) light box, and sanded lightly with 600-gritsandpaper to remove flash from the molding process. After storing indistilled water at 37° C. for 24 hours, the Flexural Strength andFlexural Modulus of the bar were measured on an Instron tester (Instron4505, Instron Corp., Canton, Mass.) according to ANSI/ADA (AmericanNational Standard/American Dental Association) specification No. 27(1993) at a crosshead speed of 0.75 mm/minute. Six bars of curedcomposite were prepared and measured with results reported inmegapascals (MPa) as the average of the six measurements.

Post-Cure Compressive Strength (CS) Test

Compressive Strength was measured according to ANSI/ADA SpecificationNo. 27 (1993). Specifically, a composition sample was heated to 85° C.,packed into a 4-mm (inside diameter) glass tube, and the tube cappedwith silicone rubber plugs and compressed axially at approximately 0.28MPa for 5 minutes. The sample was light cured for 90 seconds by exposureto two oppositely disposed VISILUX Model 2500 blue light guns (3M Co.)and then irradiated for 180 seconds in a Dentacolor XS light box(Kulzer, Inc.). The cured sample was then cut on a diamond saw to formcylindrical plugs 8-mm long for measurement of CS. The plugs were storedin distilled water at 37° C. for 24 hours prior to testing. Measurementswere carried out on an Instron tester (Instron 4505, Instron Corp.) witha 10-kilonewton (kN) load cell. Five plugs of cured composite wereprepared and measured with results reported in MPa as the average of thefive measurements.

Post-Cure Diametral Tensile Strength (DTS) Test

Diametral Tensile Strength was measured according to ANSI/ADAspecification No. 27 (1993). A composition sample was compressed in aglass tube and cured as described above for the Compressive StrengthTest. The cured sample was then cut into discs 2.2-mm long formeasurement of DTS. The disks were stored in water as described aboveand measured with an Instron tester (Instron 4505, Instron Corp.) with a10-kN load cell at a crosshead speed of lmeter/minute. Five discs ofcured composite were prepared and measured with results reported in MPaas the average of the five measurements.

Abbreviations/Definitions

BHT 2,6-Di-tert-butyl-4-methylphenol (Sigma-Aldrich Fine Chemicals, St.Louis, MO) BisGMA 2,2-Bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane CAS No. 1565-94-2 CPQCamphorquinone (Sigma-Aldrich) EDMA Ethyl 4-(N,N-dimethylamino)benzoate(Sigma-Aldrich) M5 Hydrophilic fumed (pyrogenic) silica (Cab-O-Sil M5,Cabot Corp. Tuscola, IL) R711 Methacryl silane-treated fumed (pyrogenic)silica (AEROSIL R-711, Degussa Corp., Parsippany, NJ) R972 Hydrophobicfumed (pyrogenic) silica (AEROSIL R-972, Degussa Corp.) ARQ Cationicsurfactant ARQUAD 2HT-75 (Akzo Nobel Chemicals, Inc., McCook, IL) TPEGNonionic surfactant Carbowax TPEG 990 (Dow, Midland, MI) STZSilane-Treated ZrO₂/SiO₂ prepared as described in U.S. patentapplication Ser. No. 09/541,417, abandoned in favor of U.S. Pat. No.6,624,211, issued on Sep. 23, 2003 (Karim) IEM 2-Isocyanatoethylmethacrylate (Sigma-Aldrich) TONE 0230 Hydroxy-terminatedpolycaprolactone (Dow) Diol TONE 0230- Reaction product between TONE0230 Diol and IEM; IEM prepared as described in U.S. patent applicationSer. No. 08/896,549, issued as U.S. Pat. No. 6,506,816 on Jan. 14, 2003(Aasen et al.) MAA Methacrylic anhydride (Sigma-Aldrich) PE-DiolPolyethylene diol (MW approximately 2500, Sigma- Aldrich) THFTetrahydrofuran Polyol PP50 Pentaerythritol ethoxylate (PerstorpSpeciality Chemicals, Toledo, OH) HEMA 2-Hydroxyethyl methacrylate(Sigma-Aldrich) DBU 1,8-Diazabicyclo[5.4.0]undec-7-ene (Sigma-Aldrich)OligoVDM Vinyl dimethylazlactone oligomer, prepared as described inExample 65 of U.S. patent application Ser. No. 09/884,173, issued asU.S. Pat. No. 6,635,690 on Oct. 21, 2003 (Abuelyaman et al.) UDMADiurethane dimethacrylate (ROHAMERE 6661-0, Monomer Polymer and DajacLabs, Inc., Feasterville, PA) BisEMA-6 Six-mole ethoxylated bisphenol Adimethacrylate (Sartomer CD541, Sartomer Co., Exton, PS) TEGDMATriethyleneglycol dimethacrylate (Sartomer Co.) DPIHFP Diphenyl IodoniumHexafluorophosphate (Johnson Matthey, Alpha Aesar Division, Ward Hill,NJ) Benzotriazole 2-(2-Hydroxy-5-methacrylyoxyethylphenyl)-2H-benzotriazole (Ciba Specialty Chemicals, Terrytown, NY) LEX110Lexorez-1150-110 polyester polyol (Inolex Chemical Co., Philadelphia,PA) LEX160 Lexorez-1150-160 polyester polyol (Inolex Chemical Co.)LEX110-IEM Reaction product between Lexorez-1150-110 and IEM; preparedas described herein LEX160-IEM Reaction product between Lexorez-1150-160and IEM; prepared as described herein THEIC-TMA Tris(2-hydroxyethyl)isocyanurate triacrylate (SR 368, Sartomer Co.) THEIC-TATris(2-hydroxyethyl) isocyanurate triacrylate (SR 290, Sartomer Co.)CHDM-DMA Cyclohexane dimethanol dimethacrylate (CD 401, Sartomer Co.)THEI(5)-IEM Reaction product (1:15:3 molar ratio) of 1,3,5-tris(2-hydroxyethyl)cyanuric acid with caprolactone and IEM prepared asdescribed herein THEI(10)- Reaction product (1:30:3 molar ratio) of1,3,5-tris(2- IEM hydroxyethyl)cyanuric acid with ε-caprolactone and IEMprepared as described herein BisGMA(5)- Reaction product (1:10:2 molarratio) of BisGMA with ε- IEM caprolactone and IEM prepared as describedherein GGDA(5)- Reaction product (1:15:3 molar ratio) of Glycerol 1,3-IEM diglycerolate diacrylate with ε-caprolactone and IEM prepared asdescribed herein

Starting Materials

Resin A

Polyethylene diol (PE-Diol, 25 grams (g)) and methacrylic anhydride (4.0ml, Sigma-Aldrich) were added to a round-bottom flask along with BHT(0.02 g) to scavenge free radicals. The flask was purged with nitrogenfor 10 minutes, and then heated with stirring overnight at 100° C. Theresulting material was poured into methanol, recovered by filtration,dissolved in hot toluene, reprecipitated with methanol, again recoveredby filtration, and dried overnight on a vacuum line. The dried solid wasdesignated Resin A. Analysis by ¹H NMR indicated complete conversion ofthe diol to methacrylate functionality.

Resin B

A 58% by weight solution of octadecyl acrylate (Sigma-Aldrich) in ethylacetate (82 g of solution), HEMA (2.5 g) and toluene (50 g) were chargedinto a 3-neck reaction vessel equipped with magnetic stirring, awater-cooled condenser, a thermocouple and a nitrogen inlet. Thesolution was heated under nitrogen to 115° C. and, with stirring,tert-butylperoxybenzoate (0.1 g, Sigma-Aldrich) dissolved in toluene (3g) was charged into the vessel. A small exotherm (temperature increaseof approximately 3-5° C.) was observed. After 30 minutes, 3.34 g of IEMin the presence of a catalytic amount of dibutyltin dilaurate (0.68 g,Sigma-Aldrich) was added in order to functionalize the pendant hydroxylunits of the resin. The resulting mixture was agitated overnight in a60° C. shaker bath. The resulting methacrylate functional resin wasisolated by precipitation with methanol and subsequent filtration. Thedried solid was designated Resin B. The methacrylate functionalizationwas confirmed by crosslinking a mixture of the HEMA-IEM adduct andisooctyl acrylate in the presence of a photoinitiator, DAROCUR 1173(Ciba-Geigy, Hawthorn, N.Y.), and exposure to UV light.

Resin C

A polycaprolactone 4-arm star resin was prepared according to thefollowing procedure. Polyol PP50 (35.6 g, 0.1 mole (mol)) andε-caprolactone (320.0 g, 2.8 mol, Sigma-Aldrich) were added to a glassvessel and heating under nitrogen to 110° C. FASTCAT 4224 (0.21 g, 0.5millimole (mmol), Atofina Chemicals, Inc., Philadelphia, Pa.) was addedand the mixture was heated at 170° C. for five hours. After cooling, atan, solid (melting point 48-52° C.) was formed, collected byfiltration, and dried. The solid had an OH equivalent weight of 709. Aportion of the solid (50.0 g, 18 mmol) was mixed with methacrylicanhydride (11.09 g, 72 mmol, Sigma-Aldrich) and BHT (0.35 g, 1.6 mmol).After heating at 100° C. for 17 hours and cooling to room temperature, atan solid was obtained. The dried solid was designated Resin C.

Resin D

To a stirred solution of OligoVDM (25 g, 1.7×10⁻¹ mol) and THF (250 ml)under nitrogen were added octadecyl alcohol (29.7 g, 1.1×10⁻¹ mol), HEMA(1.5 g, 1.2×10⁻² mol), and DBU (0.2 g, 1.3×10⁻³ mol). The resultantsuspension was heated to 40° C. and maintained at this temperature withstirring overnight for approximately 12 hours. The resultingyellow-orange viscous liquid was isolated by pouring into methanol andevaporation of the methanol/THF solvent at 80° C. for 12 hours under avacuum. The dried material was designated Resin D.

THEI(10)-IEM

In a 250-ml 3-neck flask equipped with a mechanical stirrer undernitrogen atmosphere, 1,3,5-tris(2-hydroxyethyl)cyanuric acid (4.30 g,0.016 mol) was suspended in ε-caprolactone (54.70 g, 0.48 mol) with acontinuous stirring. A few drops of tin(II) ethyl hexanoate were addedand the mixture was heated at 130-150° C. overnight. A clear yellowliquid was obtained. The reaction temperature was lowered to 50° C. andthen BHT (50 mg) was added followed by 5 drops of dibutyltin dilaurate.IEM (7.66 g, 0.049 mol) was then charged at 50° C. over 45 minutes.After 20 minutes of stirring, the heat was turned off. The liquidsolidified into a material that was characterized by IR, NMR and GPC.(Mw=6.46E+03, Mn=5.69E+03, P=1.14)

THEI(5)-IEM

This product was prepared as described for THEI(10)-IEM, except theamount of ε-caprolactone was halved to 27.35 g, 0.24 mol. The resultingproduct was isolated as a solid that was characterized by IR, NMR andGPC. (Mw=4.36E+03, Mn=2.859E+03, P=1.53)

BisGMA(5)-IEM

This product was prepared as described for THEI(10)-IEM, but utilizing adry air atmosphere and the reactants Bis GMA (18.50 g, 0.036 mol),c-caprolactone (42.10 g, 0.369 mol), and IEM (11.6 g, 0.074 mol). Theresulting product was isolated as a solid that was characterized by IRand NMR.

GGDA(5)-IEM

This product was prepared as described for BisGMA(5)-IEM, but utilizinga dry air atmosphere and the reactants glycerol 1,3-diglycerolatediacrylate (triglycerol diacrylate), c-caprolactone, and IEM. Theresulting product was isolated as a solid.

LEX110-IEM

A mixture of 20.0 g (20 mmol) LEXOREZ-1150-110, 6.24 g (40 mmol)2-isocyanatoethyl methacrylate, 70 g acetone, and 0.03 g (0.05 mmol)dibutyltin dilaurate was heated to 50° C. for 5 hours. The solvent wasthen removed under reduced pressure to provide the product as a whitesolid.

LEX160-IEM

A mixture of 20.0 g (28 mmol) LEXOREZ-1150-160, 8.57 g (55 mmol)2-isocyanatoethyl methacrylate, 70 g acetone, and 0.03 g (0.05 mmol)dibutyltin dilaurate was heated to 50° C. for 5 hours. The solvent wasthen removed under reduced pressure to provide the product as a whitesolid.

Examples 1-14 and Comparative Example 1 (CE-1) Self-SupportingLight-Curable Composites

Self-supporting, light-curable composites (Examples 1-14 and ComparativeExample 1) were prepared according to the following procedure. Thephotoinitiator components were initially dissolved in bisGMA, UDMA, orbisGMA/UDMA/bis-EMS6/TEGDMA blend in a water bath. Then the ingredients(names and quantities for each example shown in Table 1) were weighedinto a MAX 20 plastic mixing cup having a screw cap (Flakteck, Landrum,S.C.) and the closed cup heated in an oven at 85° C. for 30 minutes. Thecup was placed in a DAC 150 FV speed mixer (Flakteck) and spin mixingcarried out for 1 minute at 3000 rpm. The cup was then reheated for 30minutes at 85° C. followed by another minute of mixing at 3000 rpm toafford the final blended composite. A similar blended composite was madewithout the photoinitiators (CPQ and EDMA) for ease of pre-cure physicalproperty testing.

TABLE 1 Bis Resin Additive GMA (Semi-Crystalline) Surfactant-(g) STZ CPQEDMA Ex. (g) (g) Fumed Silica- (g) (g) (phr*) (phr) CE-1 4.0 — — 16.00.25 1.0 1 3.8 — ARQ-0.2 15.8 0.25 1.0 R972-0.2 2 2.0 TONE0230-IEM --2.0 — 16.0 0.25 1.0 3 2.0 TONE0230-IEM -- 2.0 ARQ-0.12 15.80 0.25 1.0M5-0.2 4 2.99 TONE0230-IEM -- 1.0 TPEG-0.12 15.72 0.25 1.0 M5-0.2 5 1.0TONE0230-IEM -- 2.99 TPEG-0.12 15.72 0.25 1.0 M5-0.2 6 2.8 Resin A --1.2 — 16.0 0.175 0.7 7 3.0 Resin B -- 1.0 — 16.0 0.188 0.75 8 2.0 ResinC -- 2.0 — 16.0 0.125 0.5 9 1.99 Resin C -- 1.99 TPEG-0.12 15.72 0.1250.5 M5-0.2 10 3.0 Resin D -- 1.0 — 16.0 0.188 0.75 11 3.8 — ARQ-0.2 16.00.25 1.0 12 1.9 TONE0230-IEM -- 1.9 TPEG-0.2 16.0 0.25 1.0 13 2.0TONE0230-IEM -- 2.0 M5-0.2 15.8 0.25 1.0 14 — TONE0230-IEM -- 4.0 — 16.00.25 1.0 15 2.4** TONE0230-IEM -- 5.6 TPE-0.24 11.5 0.25 1.0 M5-0.4*phr—Parts per hundred parts of resin (resin = BisGMA + Resin Additive)**In Example 15, UDMA was used in place of BisGMA

Example 15 Dental Impression Tray Preparation and Simulated Use

A self-supporting, light-curable composite was prepared according to theprocedure described in Examples 1-14 with the names and quantities foreach ingredient used in this Example 15 shown in Table 1.

The bulk composite was pressed in a Carver press between two siliconizedpaper liners (TPK 7120, 3M Co.) to a thickness of approximately 2 mm andheated to 40° C. The two paper liners were discarded and the sheet waslaminated manually under hand pressure at 40° C. between two layers of anonwoven fabric (SONTARA 8010, DuPont, Old Hickory, Tenn.). While stillwarm, a 10-cm×10-cm sheet of the resulting laminate was placed over astone model of a lower jaw, shaped to fit the contour loosely, andallowed to cool down to room temperature overnight. The contoured formwas carefully removed from the model and cut into the shape of animpression tray including a handle to provide a self-supporting,malleable and curable custom tray.

After several days of storage at room temperature the use of the customtray was simulated on the stone model of the lower jaw. Several layersof wet Kleenex tissue paper were first placed along the complete arch,followed by placing the custom tray on top. Custom fitting was easilyachieved by applying simple finger pressure along the whole length ofthe tray. Then the tray was tack cured for 20 seconds with a VISILUXModel 2500 curing light (3M Co.), followed by further cure for 180seconds in a Dentacolor XS unit (Kulzer, Inc.). A hard, rigid, toughtray was thereby obtained.

This tray was then filled with Imprint II Monophase ImpressioningMaterial (3M Co.) and pressed against the stone model (without the layerof the tissue paper) and retained in place until the impression materialhardened. At this point the tray, together with the hardened impressionmaterial, was separated from the stone model to obtain the impression ofthe whole arch. Excellent adhesion was observed between the hardenedimpression material and the non-woven surface of the tray.

Examples 16-32 Self-Supporting Light-Curable Composites

Self-supporting, light-curable composites (Examples 16-32) were preparedaccording to the procedure described for Examples 1-14 with theingredient names and quantities for each example shown in Table 2).

TABLE 2 Bis Resin Additive GMA (Semi-Crystalline) Surfactant-(g) STZPhoto- Ex. (g) (g) Fumed Silica-(g) (g) initiator 16 1.95 LEX 160-IEM -1.95 TPEG-0.12 15.13 PI#1** M5-0.468 17 2.93 LEX110-IEM - 0.98 TPEG-0.1215.13 PI#1 M5-0.468 18 2.7* TONE0230-IEM -- 0.9 ARQ-0.11 14.80 PI#2***R972-0.54 19 2.52 TONE0230-IEM -- 1.18 TPEG-0.11 14.36 PI#2 R711-0.44 202.93 THEI(10)-IEM - 0.98 TPEG-0.12 15.21 PI#1 M5-0.39 21 1.95THEI(5)-IEM - 1.95 TPEG-0.12 15.13 PI#1 M5-0.468 22 1.99 BisGMA(5)-IEM-- 1.99 TPEG-0.12 15.72 PI#1 M5-0.20 23 1.99 GGDA(5)-IEM -- 1.99TPEG-0.12 15.72 PI#1 M5-0.20 24 2.93 THEIC-TMA - 0.98 TPEG-0.12 15.13PI#1 M5-0.468 25 1.95 THEIC-TA -- 1.95 TPEG-0.12 15.13 PI#1 M5-0.468 262.93 THEIC-TA -- 0.98 TPEG-0.12 15.13 PI#1 M5-0.468 27 2.52* CHDM-DMA --1.08 TPEG-0.11 14.90 PI#2 M5-0.432 28 3.50* None TPEG-0.11 14.47 PI#2M5-0.4375 29 3.50* None TPEG-0.11 14.39 PI#2 M5-0.5250 30 3.24*TONE0230-IEM -- 0.36 TPEG-0.11 15.16 PI#2 M5-0.18 31 3.24* TONE0230-IEM-- 0.36 TPEG-0.11 14.89 PI#2 M5-0.45 32 3.24* THEI(10)-IEM -- 0.36TPEG-0.11 14.89 PI#2 M5-0.36 *In Examples 18 and 27-32, a resin blendwas used in place of BisGMA. The blend consisted of BisGMA (25%), UDMA(35%), BisEMA-6 (35%), and TEGDMA (5%). **PI#1 - Blend of CPQ (0.25 phr)and EDMA (1.0 phr) [phr—parts per 100 parts of bisGMA andsemi-crystalline resin). ***PI#2 - Blend of CPQ (0.176 phr), EDMA (1.55phr), DPIHFP (0.517 phr), BHT (0.155 phr), and Benzotriazole (1.552phr).

Sample Evaluations (Examples 1-14, 16-32, and Comparative Example 1)

Composite samples (Examples 1-14, 16-32, and Comparative Example 1) wereevaluated for pre-cure elastic and viscous moduli, for pre-cure crownformation, and for post-cure flexural strength, flexural modulus,compressive strength, and diametral tensile strength according to theTest Methods described herein. All samples passed the Pre-Cure CrownFormation Test, except for the Comparative Example 1 sample that wasvery soft and not self-supporting. Results from the other evaluationsare provided in Table 3 (Examples 1-14 and Comparative Example 1) andTable 4 (Examples 16-32).

TABLE 3 G′ G″ kPa Flexural Compressive Diametral Tensile Flexural Ex.(at 0.005 Hz) Strength, MPa Strength, Mpa Strength, MPa Modulus, MPaCE-1 1.4 2.3 133 (21) 277 (26) 44 (6) 7933 (805) 1 127 108 134 (15) 323(13) 42 (6) 8487 (678) 2 95 80 115 (12) 340 (19)  52 (11) 5275 (630) 3577 350 121 (12) 319 (21) 44 (6) 5169 (726) 4 138 120 168 (13) 328 (38)42.5 (7)  8928 (194) 5 3080 2410 122 (10) 284 (16) 26 (8) 4551 (449) 6624 303 109 (7)  171 (25) 28 (2) 5146 (356) 7 1890 947 107 (18) 263 (13)24 (3) 7359 (777) 8 213 156  79 (15) 298 (12) 42 (4) 3410 (354) 9 557357 87 (8) 272 (31)  46 (13) 3121 (224) 10 268 203  85 (25) 233 (12) 33(8)  5688 (1069) 11 88 73 120 (4)  299 (12) 39 (7) 6429 (608) 12 232 146 86 (12) 356 (6)  54 (7) 3943 (204) 13 520 224 137 (8)  318 (22)  45(10) 5430 (742) 14 2120 1610  76 (10) 296 (16)  45 (16) 1960 (363)(Numbers in Parentheses are Standard Deviations)

Example 1, in comparison with Comparative Example 1, shows that theaddition of fumed silica and surfactant to the bisGMA significantlyincreased the elastic and viscous moduli of the resulting composite andthereby changed the physical nature of the composite from very soft toself-supporting. As shown in FIG. 2, the elastic and viscous moduli (G′and G″, respectively) are increased from approximately 10³ (forComparative Example 1) to approximately 10⁵ Pascals (Pa) (for Example1). This suggests that the Example 1 composite has properties at roomtemperature more similar to those of the dental baseplate wax shown inFIG. 1. Furthermore, the frequency dependence of the moduli of Example 1is reduced, indicative of a more solid-like character similar to that ofthe dental waxes. It is noted that unlike a dental wax that transformsabove its melting point to a free-flowing liquid, the compositions ofthe present invention soften, but do not become free-flowing fluids(i.e., liquids) above their melting points or melting ranges.

Examples 2-5, in comparison with Comparative Example 1, show that theaddition of TONE 0230-IEM light-curable polymer to the bisGMAsignificantly increased the elastic and viscous moduli of the resultingcomposite and thereby changed the physical nature of the composite fromvery soft to self-supporting. Additionally, it can be concluded from theresults in Table 3 that further addition of surfactant/fumed silicaingredients increases the moduli, and that the moduli increases withincreasing amounts of TONE 0230-IEM polymer. It is theorized that theseenhanced properties are due to the crystalline nature of the TONE0230-IEM polymer.

Examples 6-10, in comparison with Comparative Example 1, show that theaddition of other types of polymers (Polymers A-D) can be added to thebisGMA in order to significantly increase the elastic and viscous moduliof the resulting composite in the same way that was achieved with theTONE 0230-IEM polymer. Comparison of Examples 8 and 9 shows the positiveeffect on moduli of adding a surfactant/fumed silica ingredient.

Example 11, in comparison with Comparative Example 1, shows that elasticand viscous moduli can be significantly increased by the addition ofsurfactant ARQ alone (with no Polymer Additive) to the bisGMA.

Examples 12-13, in comparison with Comparative Example 1, show thatelastic and viscous moduli can be significantly increased by theaddition of TONE 0230-IEM polymer plus surfactant TPEG (Example 12) orplus fumed silica M5 (Example 13) to the bisGMA.

Example 14, in comparison with Comparative Example 1, shows that elasticand viscous moduli can be significantly increased by the utilization ofhigh levels TONE 0230-IEM polymer alone (with no BisGMA). Followingcuring, all samples (Examples 1-14) were converted into a hard, toughmaterial having adequate flexural modulus and flexural strength,compressive strength, and diametral tensile strength to be useful as adental article, e.g., as a dental crown.

TABLE 4 G′ G″ kPa Flexural Compressive Diametral Tensile Flexural Ex.(at 0.01 Hz) Strength, MPa Strength, MPa Strength, MPa Modulus, MPa 16732 358 125 (14) 356 (6)   72 (11) 4380 (199) 17 707 363 130 (15) 358(11) 74 (5) 6649 (325) 18 547 264 141 (11) 348 (7)  65 (5) 6125 (473) 19525 257 142 (8)  368 (11) 66 (6) 7929 (380) 20 712 349 135 (14) 363 (10) 66 (13) 5533 (343) 21 1377 652 109 (10) 329 (21) 85 (4) 3348 (355) 22416 210 114 (10) 348 (11) 68 (3) 5098 (299) 23 1136 507 105 (12) 350(11)  64 (11) 5289 (251) 24 291 156 131 (13) 317 (14) 82 (3) 9864 (454)25 433 225 155 (14) 407 (23)  82 (12) 12497 (421)  26 325 179 136 (14)374 (12) 62 (3) 11920 (574)  27 1353 630 153 (18) 375 (13) 70 (7) 9088(365) 28 132 81 173 (15) 378 (14)  83 (8.2) 10299 (786)  29 291 138 172(7)  385 (13) 93 (7) 10079 (477)  30 98.5 49 157 (16) 381 (25) 92 (5)7604 (491) 31 180 94.4 147 (13) 388 (19) 82 (9) 6896 (392) 32 146 73.6151 (7)  352 (16)  80 (10) 7547 (403) (Numbers in Parentheses areStandard Deviations)

It can be concluded from the results shown in Table 4 that, followingcuring, all samples (Examples 16-32) were converted into a hard, toughmaterial having adequate flexural modulus and flexural strength,compressive strength, and diametral tensile strength to be useful as adental article, e.g., as a dental crown.

Sample Evaluations (Crystallinity and Packability)

In addition to the testing results provided in Tables 3 and 4; Examples2, 3, 13, 14, 24, 25, and 26; and the commercial material REVOTEK LCResin (GC Dental Products Corp., Japan) were confirmed to contain acrystalline component having a melting point above 20° C. when evaluatedaccording to the Pre-Cure DSC Test Method described herein. A sample ofthe commercial material SUREFIL High Density Posterior Restorative(Dentsply) showed the presence of a crystalline component having amelting point below 20° C. That is, there is no crystalline component asdefined herein. In contrast, DSC evaluations of Example 1 and thecommercial materials PRODIGY Condensable Composite Restorative System(Kerr, Orange, Calif.) and TRIAD Visible Light Cure Provisional Material(Dentsply Caulk, Milford, Del.) suggested the absence of any crystallinecomponent. The results of these DSC measurements are provided in Table5. The Elastic Moduli (G′) and Viscous Moduli (G″) of the fourcommercial materials (according to the Test Method provided herein,except that samples were pressed without heating) are also provided inTable 5.

TABLE 5 G′ G″ Crystalline kPa Melting Point Range (° C.) ComponentExample (at 0.01 Hz) (Peak Exotherm (° C.)) (at 22° C.) 1 NM* NM NoMelting Point No 2 NM NM 27-43 (36.9) Yes 3 NM NM 29-43 (36.9) Yes 13 NMNM 27-43 (37.4) Yes 14 NM NM 29-43 (36.9) Yes 24 NM NM Broadly from 0-35(no Yes peak) 25 NM NM Broadly from 0-35 (no Yes peak) 26 NM NM Broadlyfrom 0-35 (no Yes peak) TRIAD 79.5 48.8 No Melting Point No PRODIGY 83.341.7 No Melting Point No SUREFIL 594 257 7-16 (11) No REVOTEK** 883 43732-75 (65.0) Yes *NM—Not Measured **REVOTEK was further determined tocontain 23% by weight inorganic filler using standard analyticaltechniques, i.e., a weighed sample was placed in a crucible, reduced toash with a Bunsen burner, and the remaining residue weighed.

Additionally, Examples 28-32 were shown to be packable compositematerials when evaluated according to the Pre-Cure Composite PackabilityTest Method described herein. Commercial materials SUREFIL Restorativeand PRODIGY Condensable Composite were also evaluated by the samePackability Test Method and determined to be packable compositematerials.

Sample Evaluation (Example 15)

The composite sample from Example 15 was evaluated for post-cureflexural strength and flexural modulus according to the Test Methoddescribed herein. Following curing the resulting hard, tough materialhad the following flexural strength and modulus values that were veryacceptable for a material to be used as a dental article, e.g., as adental impression tray. Flexural Strength=66 MPa (Standard Deviation=5)and Flexural Modulus=915 MPa (Standard Deviation=115).

The complete disclosures of the patents, patent documents, andpublications cited herein are incorporated by reference in theirentirety as if each were individually incorporated. Variousmodifications and alterations to this invention will become apparent tothose skilled in the art without departing from the scope and spirit ofthis invention. It should be understood that this invention is notintended to be unduly limited by the illustrative embodiments andexamples set forth herein and that such examples and embodiments arepresented by way of example only with the scope of the inventionintended to be limited only by the claims set forth herein as follows.

1. A method of preparing a preformed dental product comprising:combining a resin system, a filler system, and an initiator system toform a mixture; and forming the mixture into a hardenableself-supporting structure having a first shape of a preformed dentalproduct; wherein the hardenable self-supporting structure having a firstshape has sufficient malleability to be formed into a second shape;wherein the filler system comprises an inorganic material comprisingnanoscopic particles having an average primary particle size of nogreater than about 50 nm; and wherein the preformed dental product isone that is provided to a dentist in a desired semi-finished shape,which is a facsimile of what the final shaped dental product is to be.2. The method of claim 1 wherein the mixture further comprises asurfactant system.
 3. The method of claim 1 wherein the filler system ispresent in the mixture in an amount of greater than 70 wt-%.
 4. Themethod of claim 1 wherein the nanoscopic particles comprise fumedsilica.
 5. The method of claim 1 wherein the preformed dental product isdimensionally stable at room temperature for at least about two weekswhen free standing.
 6. The method of claim 1 wherein the preformeddental product is a preformed crown, a preformed inlay, a preformedonlay, a preformed bridge, a preformed veneer, a preformed maxillofacialprosthesis, a preformed orthodontic appliance, a preformed toothfacsimile, or a preformed tooth splint.
 7. The method of claim 6 whereinthe preformed dental product is a preformed crown.
 8. The method ofclaim 1 wherein the initiator system comprises one or morephotoinitiators.
 9. The method of claim 1 wherein the resin systemcomprises a mono-, di-, or poly- (meth)acrylate.
 10. The method of claim9 wherein the resin system comprises bisphenol A glycidyl methacrylate.11. The method of claim 1 wherein the resin system comprises acrystalline component.
 12. The method of claim 11 wherein thecrystalline resin component comprises polyesters, polyethers,polyolefins, polythioethers, polyarylalkylenes, polysilanes, polyamides,polyurethanes, or combinations thereof.
 13. The method of claim 12wherein the crystalline resin component comprises a polycaprolactone.14. A method of preparing a preformed dental product comprising:combining a resin system, greater than 70 wt-% of a filler system, andan initiator system to form a mixture; with the proviso that if thefiller system comprises fibers, the fibers are present in an amount ofless than 20 wt-%, based on the total weight of the composition; andforming the mixture into a hardenable self-supporting structure having afirst shape of a preformed dental product; wherein the hardenableself-supporting structure having a first shape has sufficientmalleability to be formed into a second shape; and wherein the preformeddental product is one that is provided to a dentist in a desiredsemi-finished shape, which is a facsimile of what the final shapeddental product is to be.
 15. The method of claim 14 wherein the mixturefurther comprises a surfactant system.
 16. The method of claim 14wherein the preformed dental product is dimensionally stable at roomtemperature for at least about two weeks when free standing.
 17. Themethod of claim 14 wherein the preformed dental product is a preformedcrown, a preformed inlay, a preformed onlay, a preformed bridge, apreformed veneer, a preformed maxillofacial prosthesis, a preformedorthodontic appliance, a preformed tooth facsimile, or a preformed toothsplint.
 18. The method of claim 17 wherein the preformed dental productis a preformed crown.
 19. The method of claim 14 wherein the initiatorsystem comprises one or more photoinitiators.
 20. The method of claim 14wherein the resin system comprises a mono-, di-, or poly-(meth)acrylate.
 21. The method of claim 20 wherein the resin systemcomprises bisphenol A glycidyl methacrylate.
 22. The method of claim 14wherein the resin system comprises a crystalline component.
 23. Themethod of claim 22 wherein the crystalline resin component comprisespolyesters, polyethers, polyolefins, polythioethers, polyarylalkylenes,polysilanes, polyamides, polyurethanes, or combinations thereof.
 24. Themethod of claim 23 wherein the crystalline resin component comprises apolycaprolactone.